I use 1024X768. I have a 'monster' CRT 17" DELL monitor. 'monster' refers to how emmensely large it is, and its heaviness. It weighs about 40 pounds.....
Sometimes i use 2580*1024 and sometimes i use 1024*768, though i usually prefer 1024*768, since the other is so tiny.
it really depens on how big your monitor i use 1152x864 becuz i can fit more stuff on the screen i think mines 17 or 19"