This should get the job done. Add an SSD for faster booting and performance.
PCPartPicker part list:
http://pcpartpicker.com/p/Krwn
Price breakdown by merchant: http://pcpartpicker.com/p/Krwn/by_merchant/
Benchmarks: http://pcpartpicker.com/p/Krwn/benchmarks/
CPU: Intel Celeron G1610 2.6GHz Dual-Core Processor ($49.99 @ Newegg)
Motherboard: Biostar H77MU3 Micro ATX LGA1155 Motherboard ($86.97 @ Newegg)
Memory: G.Skill 4GB (2 x 2GB) DDR3-1333 Memory ($28.99 @ Newegg)
Storage: Hitachi 500GB 3.5" 7200RPM Internal Hard Drive ($59.99 @ Newegg)
Case: Rosewill FBM-01 MicroATX Mini Tower Case ($34.98 @ Newegg)
Power Supply: Corsair Builder 430W 80 PLUS Bronze Certified ATX12V Power Supply ($34.99 @ Newegg)
Optical Drive: Samsung SH-224BB DVD/CD Writer ($17.99 @ Newegg)
Total: $313.90
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-03-17 23:26 EDT-0400)