Which is the heaviest present day lifter (rocket)? And is it comparable to the Saturn V rocket? I know of the Ariane 5 ECA, the Delta IV rocket and a few more, but which of the present day's rockets is the top heavy lifter, say, to low Earth orbit (LEO)?
Although it is not a certain fact, I would imagine that a very heavy lifter to LEO is also good for placing objects into geostationary transfer orbit (GTO) and could be a good candidate for out of Earth orbit flight (for instance a trip to the Moon). 
 A: The Saturn V payload mass to LEO was 118,000 kg. Wikipedia has a decent comparison of Super-heavy launch systems with a payload mass to LEO of 50,000 kg or more. None are in current use, and only two systems are in development.
There is also a "Heavy" lift launch system list which includes the Delta IV and Ariane 5 you mentioned. The top operational system is the Atlas V HLV with a mass to LEO of 29,420 kg and a Mass to GTO of 13,000. However, it has never been launched and the United Launch Alliance claims it needs a 30 month lead-time to produce the Heavy Launch Vehicle variant of the Atlas V.
Next on the list with mass to LEO/GTO:


*

*Delta IV Heavy: 22,950/12,980 kg, 3/4 successful launches.

*Proton: 21,600/6,360 kg (comparatively lower GTO due to launch location), 295/335 successful launches

*Ariane 5: 21,000/10,050 kg, 54/58 successful launches.


So the answer is there are no currently operational launch systems which approach the Saturn V Mass to LEO capability.
A: The Falcon Heavy seems to be available 2014: http://www.spacex.com/falcon_heavy.php
It will lift 53000 kg from Cape Canaveral to LEO.
A: It is Mar 2017. Falcon Heavy is still at least 6 months away. But as far as planned vehicles go there is a new behemoth named ITS which should be available sometime in next decade.
