If your planning on overclocking then get some good low latency, high speed ram that will do 300 mhz(actual speed) or more.
If your not overclocking then normal pc3200 will do.
I have used corsair and crucial value ram and havent had any problems with it. I dont overclock so dont need the high end ram.
2 gigs is getting close to the normal now.
Its best to use 2 sticks total so go with 2x512 or 2x1 gig sticks for dual channel support.