Learning physics online? I'm thinking of following some kind of education in physics online. I have a master degree in Computer Science and have reasonable good knowledge in physics. I would like a program of 1-2 years and I'm more interested in particle physics. 
Is there any good online program that offer something similar?
 A: My main piece of advice to someone asking this question is: don't skip the basics.  It's very tempting to try to skip right to something sexy: field theory, general relativity, string theory, etc.  Avoid this temptation and take a slow, methodological approach. 
Since you say you have a good background in physics, however, you might be able to pick up David Griffiths' undergraduate particle physics textbook immediately.
If you were starting out from zero, I would suggest: spend six months or a year reading the three-volume set of the Feynman lectures and working out the problems.  Spend six months each working through Griffiths' quantum mechanics textbook, an analytical mechanics textbook, a thermal physics textbook, and an E&M textbook.
Something that works well for me, and as a computer scientist, might work well for you, is to try to simulate physical scenarios numerically in addition to solving them analytically (as in the textbooks).  Working with a numerical model and seeing how it agrees or disagrees with the formal theory is often quite illuminating.
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*NPTEL has a bunch of undergrad review level physics and math courses in the Basic Courses category.

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*ICTP has a lot of high-undergrad and graduate-level courses, including condensed matter and HEP.

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*UCCS has a large collection of online math courses - some very useful.


Good luck! (And sorry the links had to be spread across multiple answers.)
A: Stanford has posted a bunch of theoretical physics courses by top physicist Leonard Susskind:
Classical Mechanics
Quantum Mechanics
Special Relativity
General Relativity
Cosmology
Statistical Mechanics
I'm a physicist but I still watched all these, just because Susskind is such a great teacher of physics. This is as good as it gets!
A: Here are a few that don't appear to have been mentioned:
[EDIT: I will list one per answer, as the spam filter won't allow me to post more than one link at a time.]


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*I second MIT's OCW as the very best resource for self-learners.

A: In general, I think the following is a fair - if a bit strongly-worded - response to your question:
"It always makes me laugh when people hope they can learn physics online. Yeah, sure you can, just as you can learn languages online but you're not going to be articulate compared to someone that is on a full time course. They live physics for years with like minded people, day in, day out. If you want to learn physics the same way someone learns a foreign language by carrying around a translation dictionary because they lack the effort required, then go right ahead. Just don't delude yourself in believing you can know what a graduate physicist knows."
There is little substitute for a full-time course of studies if you really want to learn physics the way a young postgraduate / PhD. student knows the subject.
However, if this option is not currently available to you, or you prefer the out-of-class method / approach, the following may be useful:
The Road to Reality: a complete guide to the laws of the universe (Vintage, 2007), R. Penrose
An excellent "roadmap" / reading-resource book to guide you from basic* mathematics to advanced-level** physics.
(* As Penrose suggests in the Preface, the only prerequisites are a familiarity with [whole numbers and] the ability to do fractions.)
(** 'Advanced-level' physics means the frontiers of modern-day research physics, e.g. loop quantum gravity, string theory, twistor theory, dynamical triangulation theory, et cetera.)
Summary:
The book is definitely NOT for casual reading: it may be best described as a roadmap for those pursuing a full-fledged undergraduate - then postgraduate - degree in theoretical physics. 
The best way to utilise it is to*: [start from the beginning, then] (i) read a specific section of a chapter dealing with a specific topic (or area if relevant); (ii) find an appropriate textbook(s) to study the topic (or area) in full detail - with problem-sets and self-administered homework, quizzes, and regular tests to help you assess your progression; then, (iii) return to step (i).
Gradually, after several years, you should have mastered the requisite materials to understand a sizable fraction of research-level physics papers, et cetera.
(* In your case, as you already have some knowledge of undergraduate-level physics, the chapters pertinent to your interests may be more relevant.)

Also, the following online resource may also be helpful:


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*How to Become a Good Theoretical Physicist;

*How to Learn Physics
For online reading materials, et cetera: (there are many, so any sites which you might find helpful / useful may be added as you like)


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*Physics Books online;

*Mathematics Books online
A: Since you say you're mostly interested in learning physics, not in a degree, there are lots of options. You say you have good knowledge of physics; if you want to learn particle physics, you need a good undergrad physics background plus some additional knowledge. I tend to think that reading textbooks is still the best way to learn the basics; if you want to learn particle physics, you might start with the book by Griffiths. If you find that you don't have enough background knowledge for it, then you would need to read other, more basic textbooks. Once you pass some threshold of background knowledge, though, you can learn a lot online. You could try searching arxiv.org for introductory lectures on various topics. In particle physics, for instance, you might search for the word "TASI", which is a summer school for graduate students to learn more about the field (the lectures are often written up and posted online). Most of this will assume you already know quantum field theory, though.
You can get a prepublication draft of Mark Srednicki's QFT textbook from his website (PDF file).
The Perimeter Institute has a one-year Master's degree program and videotapes all of the lectures. You can watch the videos from their archive.
A: List of recommended books and notes from the beginner level to advanced:
How to Become a Good Theoretical Physicist
Similar list on mathematics, parts of it may be useful for physics too:
How to Become a Pure Mathematician (or Statistician)
MIT OCW offers complete courses in Classical Mechanics, Electricity and Magnetism and others, designed for independent students. Tens of other physics courses are available, but may not be complete.
A: Khan Academy has a bunch of great online lessons - in the Physics section - too many to count - probably about a hundred or so.
http://www.khanacademy.org/
A: It always makes me laugh when people hope they can learn physics online. Yeah, sure you can, just as you can learn languages online but you're not going to be articulate compared to someone that is on a full time course. They live physics for years with like minded people, day in, day out. If you want to learn physics the same way someone learns a foreign language by carrying around a translation dictionary because they lack the effort required, then go right ahead. Just don't delude yourself in believing you can know what a graduate physicist knows.
Let me put it another way:
A physicist on a full time course might spend at least 50 hours a week learning about physics. How much time do you have to spare?
A: If you are familiar with the general physics (first year of science and engineering schools; i.e., I mean 105-106 not the 101-102 or 103-104) you can jump start to become a real theoretical physicist by reading Feynman's Lectures on Quantum Mechanics. This beautiful book made me courageous to talk about physics. If you find some referral to basics that you cannot understand then go to the previous volumes of his basic lectures on university physics; just read them. Feynman is a bit boring since he expects some commitment and vehemence from the reader (he gagues your real interest to physics vs your whim) but once you fall on his track then you can follow his fast pace. He teaches everything you need as a future physicist in the same place. You are not a physicist if you do not know mechanics as much as Goldstein's and electrodynamics as much as Jackson's books. Happily all these books are available free by bit-torrent sharing of resources on-line.
A: As most of the people have mentioned the best way to learn physics is from textbooks, and then resolve the doubts from the Internet. But, if you face difficulty in getting access to books, then there are a number of excellent free lectures notes on line. As you would need to start with the basic classical mechanics, relativity and statmech and later QFT. The lectures by david tong are an excellent resource. 
http://www.damtp.cam.ac.uk/user/tong/qft.html
For Quantum Mechanics, I have been very much impressed by the online video lectures and notes of James Benny at Oxford. He has also written a lecture notes on other topics. 
http://www-thphys.physics.ox.ac.uk/people/JamesBinney/lectures.html
There are the notes of Srednicki for QFT mentioned above. After having mastered CM, QM, QFT(a bit), read a bit of representation theory, and move on to the particle physics.
A: No list would not be complete without reference to Richard Feynman lectures.
I wished I could have watched them sooner. 
My favorite is his The Vega Lectures
A: For some practice exercises you may also consider Physics is Beautiful, which is like Duolingo but for physics. As far as learning particle physics, Griffiths Introduction to Elementary Particles is a very good book. The cover looks a bit intimidating in my opinion, but it reads like a novel, in a good way. We used it in the undergrad particle physics course I took at Berkeley. 
A: I am a high school physics teacher in NY State. I made a bunch of videos for my students which I have in turn made available online for others. 
My courses are all focused on the AP Physics curriculum, specifically AP Physics 1 (though AP Physics 2 courses are slowly coming out). I host all of my content on my own site. You will find a ton of content covering all aspects of physics.  60+ hours of video lessons, 100’s of worksheets, all sorts of great stuff! 
www.physicscourseonline.com
