I agree Asus motherboards are the best, for RAM you will want Corsair or Crucial. 512mb is satisfactory but you ideally should get 1GB. and should be pc-3200 at least. RAM is not that expensive.
For cpu generally AMD is better for gaming than intel, don't know the specifics but that seems to the overriding opinion (Athlon 64-bit btw)
You need to find out if the Cpu and graphics card will work with your board, but you should probably replace that anyway if you are upgrading those. For video cards any of the newer nvidia cards are great.
fsb is front side bus, term for the physical bi-directional data bus that carries all electronic signal information between the Cpu and other devices within the system such as RAM, the system BIOS, AGP video cards, PCI expansion cards, hard disks, etc.
Oh sonomaa I don't like microstar (msi) boards but that's just me
. Asus by far the best Ive had.