According to that board's specs, it can have:
No more than a 4GB stick in each slot
Speed must be no higher than 1333MHz DDR2.
That's all you need to take into consideration with the RAM.
If you're thinking of buying RAM for that board, a set of 2x2GB 1066MHz RAM should be fine for you unless you need more.
Also, if there are strict compatibility requirements for video cards, what are those? Thanks guys!
There are very strict requirements but only one, which is the type of slot. Nearly all cards nowadays use PCI-E x16 slots, but there is an older slot called AGP which occasional pops up around here sometimes. I don't think any AGP cards are manufactured nowadays. They are not interchangeable.
There are two versions of PCI-E x16, 1.0 and 2.0. They are interchangeable, the 2.0 is just faster. All current cards work with either version, though in future eventually cards will need more bandwidth than 1.0 can provide. The motherboard you linked to has two PCI-E x16 1.0 slots and does Crossfire (multiple ATi GPUs).