Here is some options to look over. I would probably go with the Abit mobo or the DS3L (for the cheapest). The DS3R is probably the most well rounded one with RAID support and more SATA ports.
Mobo - $98 shipped - $20 MIR (if you trust MIR’s) = $78 Hard to beat at this price.
ABIT IP35-E INTEL P35 CHIPSET ATX FORM FACTOR 1xPCI-E(X16)/2xPCI-E(X1)/3xPCI/4xDDR2 W/SATA2,LAN(Gb),USB 2.0 & AUDIO
http://www.mwave.com/mwave/skusearch.hmx?&scriteria=BA2...
Mobo - $106 shipped Good reviews and OC’s well, hard to beat at this price.
GIGABYTE GA-P35-DS3L LGA 775 Intel P35 ATX Intel Motherboard - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Mobo - $137 shipped As good as DS3L, but has RAID and more SATA ports
GIGABYTE GA-P35-DS3R LGA 775 Intel P35 ATX Intel Motherboard – Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Pick any one of these memory selections and you will be fine, including OC'ing them too.
Memory - $102 shipped - $40 MIR = $62!! Solid performing CAS 4 DDR2
CORSAIR XMS2 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory – Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Memory - $110 shipped - $47 MIR = $63!! Good OC’ing RAM + CAS 4 too.
Crucial Ballistix 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory – Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Memory - $93 shipped - $30 MIR = $63!! CAS 4 and good RAM
GeIL 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory - Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Also a case to consider and a good PSU for powering that rig up!
PSU - $100 shipped - $45 MIR = $55, can’t beat for this price
Antec NeoPower NeoHE 550 ATX12V 550W Power Supply 100 - 240 V UL, CUL, TUV, CE, FCC, CCC, CB, C-tick – Retail
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Case - $40 shipped - $10 MIR = $30!! Can’t beat the quality and price on this one.
COOLER MASTER Elite 330 RC-330-KKN1-GP Black SECC ATX Mid Tower Computer Case – Retail
http://www.newegg.com/Product/Product.asp?item=N82E1681...
Not sure if any of this helps, but I thought I'd throw it out there for ya.
My 2cp's