There are many different versions of the Atlas V. Here's a link to the non-Heavy versions that lists their payload capacities. Here's another source that lists payload capacity of the different Atlas V versions for GTO and GEO.

Here's some good Atlas V info.

As for Atlas V missions out of Vandenberg, most launches there are for polar orbit (e.g. Iridium) or sun-synchronus orbit (e.g. DMSP, NPOESS, and imagery satellites). There will still be launches into both types of orbits in the future, so you can bet that some of them will go on some version of the Atlas V. The NRO may not be building many more of the monster sized satellites in the future because of a new series of satellites they're working on, but they're a pretty close-lipped organization who keeps such details closely held.

Funny thing, when I Googled +"Atlas V Heavy" +payload, this was one of the hits.