Also, I recommend the series over on C&V on buying a basic bike:

Brands to seek, brands to avoid.
http://www.bikeforums.net/showthread...brands-to-seek

Type of Bike:
http://www.bikeforums.net/showthread...ype-of-bicycle

Condition:
http://www.bikeforums.net/showthread...ting-condition

Signs of quality/components:
http://www.bikeforums.net/showthread...y-poor-quality