http://www.bikesdirect.com/
These guys make bikes with leftover components from good bike companies. They then slap a frame on them and you get discount prices. The frame might say Motobecane, but it has the same components as a Trek, Cannondale, Specialized etc. You might pay $200 for what would be a $400 bike with a pretty name on it.
Otherwise, used is the way to go!