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Have you ridden anything other than the stationary bike recently or at all? And do you know what size of frame you will need? If you answered "no" to either or both of those questions, you should start by going to various bike shops and doing test rides of entry level models of the various categories- road, HT MTB, hybrid (rigid would likely be better than front suspension). This will give you an idea of what style your body prefers* and what size you should be looking at.

*A bunch of bikes look damned sexy to your brain, but your body will give you a reality check. For example, I really dig a certain model online, but when I found one in my size at the LBS, it just didn't feel right.