Intel Core i7 920 is the best bang for the buck processor wise.
http://www.newegg.com/Product/Product.a ... 6819115202
CPU Cooler (Optional, stock is fine but I prefer bigger, quieter aftermarket fans)
http://www.newegg.com/Product/Product.a ... 6835608014
Asus P6T motherboards are very solid.
http://www.newegg.com/Product/Product.a ... 6813131359
Corsair XMS3 6GB DDR3 memory set is good value for the money
http://www.newegg.com/Product/Product.a ... 6820145220
Western Digital VelociRaptor 300GB hard drive for disk i/o performance. Unless you have a little bigger budget, then spend an extra $100 on either a Corsair or a G.Skill Falcon SSD drive (Make sure it's 220/MB Read 190/MB Write, there are many versions). The SSD will perform like nothing you've ever seen before, but you will want to offset it with a traditional hard drive for your day to day disk writes (like internet cache files and stuff like that).
VelociRaptor:
http://www.newegg.com/Product/Product.a ... 6822136322
SSD:
http://www.newegg.com/Product/Product.a ... 6820233087
Case - Up to you, but all the machines I build use this one. It's a full tower case (Translation: Fucking huge), but it's got a ton of air flow and if you live in a warm climate, it won't overheat on you.
http://www.newegg.com/Product/Product.a ... 6811133021
Video Card - eVGA GTX275 is the highest performer for a non-SLI card
http://www.newegg.com/Product/Product.a ... 6814130475
Power Supply - Any 600W+ unit is good, I prefer Silencer 750's from PC Power and Cooling. Never had one fail on me, and I use them in every system I have, and they are nearly impossible to hear, hence the name.
DVD Burner - Up to you, just make sure it's a SATA drive, I use these:
http://www.newegg.com/Product/Product.a ... 6827106289
That's about it, naturally keyboard/mouse/monitor/Operating System are also up to you.
If you want to see a set of machines I've built, using parts like this, check this link out. Almost all of them use the same style of design.
http://www.agonyguild.net/vbox/
-V