EVGA 600B 600W 80+ Bronze Certified Power Supply
Price: $49.49 at SuperBiiz
The power supply is what provides power to all of the components in your computer. This is another one of those parts that you don't want to skimp on. If you buy a no-name power supply that you got for super cheap, it's very likely that you will burn it out and in some cases, set your computer on fire.
It's important to note that when choosing your power supply, you will need to make sure that the power that all of your parts will draw does not exceed the wattage rating that your power supply can put out. Overloading your power supply can lead to serious problems.
The power supply I have recommended here is one of the most common power supplies I've seen in budget builds. It provides more than enough power to run all of your components -- and has some power to spare. That way, if you want to upgrade to more powerful hardware, you may not have to go out and get a new power supply to support it.