I am not sure if you live in the US or Canada, but here are some suggestions on stuff available at Newegg (US, but there is a Canadian site also).
Chassis
Your choice - ~$60
Motherboard
GIGABYTE Z68P-DS3 - $100
Processor
Intel Core i3-2100 - $125
Memory
Corsair Vengeance 8GB (2x4GB) - $50
Graphics
Radeon HD 6770 - $110
Power Supply
Corsair Builder CX430 - $50
Hard Drive
Western Digital 500GB Caviar Blue - $110
The sub-total of all this is $605 (no shipping or taxes), and I admit that some of the parts are not ideal. You're planning to build a PC at a bad time due to the recent increase in hard drive prices as marfig and TCS mentioned, but that one I picked there is about as good as I could find without sacrificing too much or going overboard.
That said, a PC like this would be able to handle current games quite well (especially at 1440x900 or 1680x1050). Someone else might have better suggestions, but I'd feel this to be quite a good PC for the cost.