Elipticals or cross gtrainers are better than stationary bikes, but getting a good one will probably fall outside your price range unless you're looking used. As mentioned, outside jogging would really be ideal (and FREE
) or some aerobics DVDs you can do at home. The Tae Bo series is great, as are many of the other aerobic series like Turbo Jam (although some use weights and/or resistance bands, you can typically make due without them). You can check your local video store for their selection and decide which ones you particularly like before byuing anything, too. Good luck!