Any DDR2-800+ should do. If you don't plan on taking your CPU past 3.6GHz (=FSB 1600MTs= RAM@800MTs, i.e. max rated speed), you're good with even some generic-brand value RAM. Since generic brand value RAM sticks don't usually OC too well (some do,some don't, you may have to loosen timings etc. largely depends on your luck whether you get a good stick or not), if you're planning on taking your CPU (way) past 3.6GHz, look for some high-performance/gaming RAM, look at some well-known brands like OCZ, Corsair, Patriot, and so on...
