Some helpful links to get you started

Above all comb through the late Sheldon Brown’s articles on everything.

Need a used bike? Check Gearin’ Up Bicycles or craigslist, and reference Bike House’s guide on buying used bikesBikepedia, and bicycle blue book

New bike? Buy exactly what you want from a friendly local bike shop (walk out if they’re pushy or not friendly) or nail down your size and buy one online from any number of sources. You can get something decent in the $200-$400 range from BikesDirect, Critical Cycles, Public Bikes, Pure Fix–There are far too many to name. One of our mechanics can help you assemble it. If you do it yourself, please don’t force the pedals into the wrong side.

Check out the Bike House’s guide on buying used bikes, Bikepedia, and bicycle blue book