This motherboard costs 74$, it's AM3+ so Bulldozer ready, it has all solid capacitors which you won't find at similar priced motherboards, USB 3.0 and Core Unlocker! The last one will help you turn your 3-Core CPU into a Quad Core! The only bad thing about this, is the SATA 3 support. But you wont see any perfomance difference with HDDs so it's pretty acceptable!
Asus Motherboard M5A78L-M LX AMD AM3+ 780GB/SB710 PCI Express SATA Microatx Retail Turbo Key
http://www.amazon.com/Asus-Motherboard-M5A78L-M-Express-Microatx/dp/B0057BRMZI/ref=sr_1_1?ie=UTF8&qid=1314132386&sr=8-1
A 3 core CPU is the less that you have to buy this days..The next one comes @ 3.2GHz which helps at gaming!
AMD Athlon II X3 450 Rana 3.2GHz 3 x 512KB L2 Cache Socket AM3 95W Triple-Core Desktop Processor ADX450WFGMBOX
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103886
Get 4GB of high speed RAM, as Bulldozers will need it.
Kingston HyperX Blu 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model KHX1600C9D3B1K2/4GX
http://www.newegg.com/Product/Product.aspx?Item=N82E16820104203
Don't get a green drive they have problems. That's the best you can get around this price as Caviar Blacks are too expensive.
Western Digital Caviar Blue WD5000AAKS 500GB 7200 RPM 16MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136073
Get a 6670. It's the least you can get for a gaming PC for me! XFX offers lifetime warranty with registration
XFX HD-667X-ZHF3 Radeon HD 6670 1GB 128-bit DDR3 PCI Express 2.1 x16 HDCP Ready Video Card
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150542
You should make an investment for PSU. Get a good one because you don't need anything that will blow up plus you can keep it for your next system!
550W are overkill for this system but, as we said, we are making an investment here!
XFX Core Edition PRO550W (P1-550S-XXB9) 550W ATX12V 2.2 & ESP12V 2.91 SLI Ready CrossFire Ready 80 PLUS BRONZE Certified Active PFC Power Supply
http://www.newegg.com/Product/Product.aspx?Item=N82E16817207013&Tpk=xfx%20550w
Case is important too, as you need everything to run nice a cool. The next one is great for it's price!
Xigmatek ASGARD II B/O CPC-T45UE-U01 Black / Orange 0.8 mm SECC / Aluminum and Aluminum Mesh Bezel ATX Mid Tower Computer Case
http://www.newegg.com/Product/Product.aspx?Item=N82E16811815006
This is a better configuration that can go pretty good, on low resolution gaming! Plus it's highly upgradeable! So when you get some $$, you can change CPU to a Quad Core Bulldozer, let's say +adding another 4gb of RAM and a better GPU and play anything!