Bike Shopping

I drove out to the city this morning and spent the day going to bike shops with Rachel. I can't stand cross training so I'm thinking of switching to biking for a while. I'm completely clueless when it comes to bikes, since the only ones I ever owned were of the cheapest kind you could possibly get and only served the purpose of getting me around. I wasn't looking to get a bike today but picked up some good information. I want to get a somewhat nicer bike but I don't know how much I'll be using it when I start running again so maybe my best bet is to look for a used one out of craigslist.