1 x USB 10 Port HUB - http://www.ebay.com/itm/New-10-Port-USB-2-0-High-Speed-Hub-AC-Power-Adapter-Black-/170855584358?pt=US_USB_Cables_Hubs_Adapters&hash=item27c7c95266

3 x Block Erupters - http://buyahash.com/?product=asic-usb-block-errupter-330mhs

Total: ~$55.00

Almost 1GH/s mining power