Does Democritus's "Atom" exist? Everything is made up of atoms, those are made up of particles like protons, neutrons and electrons. protons and neutrons are made up of quarks, is there a limit to this or can it go on for ever?
Was Democritus right or wrong when he said if you kept dividing something on and on you would get to a point where dividing further won't be possible.
 A: Ooo, I like this question.
True we use "atom" to mean something on the periodic table but those are divisible, and have a structure.
To date the standard model seems like a good model. In that model there are a finite number of elementary quarks, leptons, and gauge bosons.  So it would seem (all known issues aside for the moment) that we are in a good position to say yes. However, we know gravity has not been successfully unified, that there are potential anomalous behaviors with GR and the standard model (SM), and string theory offers a model that predicts what we know as seems to unify GR and QFT-SM.
What Democritus meant in his mind when he defined Atom may not be what we know to be indivisible units of matter.  Democritus may have been thinking of something that is finite in extent (not sure, been a long time since I've read about it) and our "elementary constituents" (as I like to call them) are Fields that are quantized.  Particle physicists think of the electron as a point particle but as a quantum field one could say its smeared out everywhere.  If you accept that Democritus meant to define Atom as an abstraction that cannot be further reduced then I'd say we have achieved that description of nature.  But in the literal sense maybe not.
Have you read Libnetz's work Monadology?  This was an influence on me in graduate school.  I believe he abstracts the concept of Atom to include greater abstraction for describing all things in terms of primitive irreducible concepts.  
A: Based on experimental measurements, quarks, leptons, and neutrinos are currently believed to be point particles, with no internal structure. In this sense, they are "indivisible." 
Typically, we infer whether there is internal structure within a particle based on scattering experiments, which can measure the form factor, which is essentially a function of the distribution of matter in the object. The form factor for a single point of matter looks different than the form factor of an extended or composite object. Quarks were actually discovered using this method. High-energy electron-proton collisions (known as "deep inelastic scattering" experiments) revealed that the proton form factor at high enough energies looked like that of a collection of point particles.
In the special case of the electron, another way to search for internal structure is to measure its electric dipole moment (EDM). A nonzero electric dipole moment would imply that the electron is an extended object of non-uniform charge density, which may be evidence of internal structure. Currently, the electron electric dipole moment has been measured to be zero with very high precision; this measurement has placed significant constraints on many beyond-the-Standard-Model theories.
A: 
Everything is made up of atoms, those are made up of particles like protons, neutrons and electrons. protons and neutrons are made up of quarks, is there a limit to this or can it go on for ever?

Sure, this can go on forever. 
However, according to the standard model of particle physics the electrons and the quarks are point particles (indivisible). 

Was Democritus right or wrong when he said if you kept dividing something on and on you would get to a point where dividing further won't be possible.

We can not say for sure whether he was right or wrong. This depends on what you mean by "dividing" as well as what you mean by "kept on."
However, according to the standard model of particle physics the electrons and the quarks are point particles (indivisible). 
