A Corsair CX550M or be quiet! Pure Power 10 550W would work in most low-med end builds but still I would still like to know your specs just to be sure.
If you don't mind rebates, great deals from the 'egg on the CXM 450w for $27 ($47 w/ a $20 MIR) and the CX 550w for $33 ($50 w/ a $20 MIR and $3 shipping)...
Look at the Corsair CX, Corsair CXM and Cooler Master MasterWatt as budget options.
If you can afford ~$60, the Bitfenix Whisper (modular), Bitfenix Formular (not modular), otherwise the Seasonic Focus 450 as an alternative, are high quality power supplies.