Here, a low-end budget system I made:
-Q8200 (or wait for Sandy Bridge @ 1st quarter 2011)
-ASRock P43DE LGA 775
-Kingston 4 GB (2 x 2 GB) of ValueRAM DDR2 5-5-5-15
-Seagate 250 GB HDD 7,200 Rpm
-Pixelview 9800GT 1 GB
-Corsair 500W PSU.
This system would total about $400. Yet still enables you play Call of Duty MW2 and Starcraft 2 smoothly at 1680x1280.