A quick thought about size. Different brands and bike geometries (how the different tubes and such are angled) give very different results from the same numbers.

Happily, many bike shops will let you go in and try their bikes out, and they'll usually have some basic ideas about what bike will fit you. Write down some notes, and then you'll get a good idea about whether you want a cruiser or a road bike, or whatever. Try lots of bikes, and don't be tempted to buy at the first shop or on the first day.

That will also be useful if you decide to buy a bike off craigslist or whatever, since you'll be able to that bike and compare it with what you've felt on other bikes.

Good luck!