Do you need a new monitor? Cause that would jack the price up by about $130.
Otherwise:
CPU:
Intel i5 3550 - $210 (don't be a fool and buy garbage AMD product... you will regret it)
Mobo:
ASRock Pro3 - $95 (Most well reviewed motherboards are fine... this is the first I looked at and it has plenty of good reviews with a low price)
RAM:
8GB - $45 (Any well-rated brand will do, they're all around the same price and performance)
GPU: None, ivybridge graphics should do just fine for non-gaming use, and even work for light gaming.
HDD:
2x WD Caviar Blue 500GB - $120 ($60 each... these are STILL crazy expensive from that flooding and won't be doing down for another few years...)
Case:
Antec Three Hundred - $55
Total: $525
+ monitor
Samsung 19.5" - $130 at costco, slightly more elsewhere
Total: ~$660