here's my stab at a budget build
Case/PSU:
http://www.newegg.com/Product/Produc...82E16811164057
CPU:
http://www.newegg.com/Product/Produc...82E16819103246
Mobo

has on board video no need for graphics card but can upgrade later)
http://www.newegg.com/Product/Produc...82E16813138038
Ram:
http://www.newegg.com/Product/Produc...82E16820161675
and you have everything else so the cost of this ^ is $110 and you have a DVD drive and HDD already and monitor/keyboard so really its like $110 and you can upgrad to a vide card/better PSU later. Then slap Linux on it ( you have many choices) and you're good.