Motherboard - $135
Gigabyte P55A-UD3:
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128412&cm_re=p55a-_-13-128-412-_-Product
CPU - $195
Intel Core i5 750:
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115215
GPU - $310
XFX Radeon 5850:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150442
RAM - $90 - $10 MIR
Patriot 4GB DDR3:
http://www.newegg.com/Product/Product.aspx?Item=N82E16820220435
Case - $60
Antec 300:
http://www.newegg.com/Product/Product.aspx?Item=N82E16811129042
PSU - $70 - $25 MIR
550W OCZ Modular:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817341022
HDD - $85
1TB Samsung Spinpoint:
http://www.newegg.com/Product/Product.aspx?Item=N82E16822152185
Optical - $30
MSI DVD/CD Burner:
http://www.newegg.com/Product/Product.aspx?Item=N82E16827100059
Total: $975 - $35 in MIR.
The way I did it: At your budget, the Core i5 is the best CPU when it comes to bang for buck. Since you likely won't be needing to crossfire/sli at this price range (and because it's not a really good solution either way), I went with a lower end motherboard from one of the two top manufacturers. Asus and Gigabyte are the two brands I trust on motherboards. MSI is supposed to be decent as well.
At $1000, the best GPU is the 58xx series by ATI. Do not bother with nVidia cards at this time. The GPU is the most important part of a gaming build.
RAM, just go to Newegg and find the cheapest 4GB set (2x2GB sticks) of DDR3 RAM that has a reputable brand behind it and a high user review. G.SKILL, Mushkin, and Corsair have great memory. Stay away from OCZ DDR3 for now.
I like the Antec 300. It's what I use. Other recommendations at this range would include the Coolermaster 690 which has more room inside I believe. Antec and Coolermaster make great cases at a variety of prices.
500W - 650W is more than enough for any processor plus single video card. I picked a modular one here which frees up cables. OCZ makes decent PSUs. I believe the best brands in Power Supplies are Corsair, Seasonic, PC Power and Cooling (owned by OCZ now) and to a lesser extend Antec.
I hear the Samsung Spinpoint F3 are the fastest HDDs around right now at a reasonable price. Also check out the 640GB and 1TB Western Digital Caviar Blacks.
CD/DVD drive really doesn't matter. I just picked the lowest priced DVD Burner with a retail box so it comes with what you need to hook it up.