If you're too cheap to pay for a personal trainer after dropping two or three hundred bucks on a new iPhone or iPod Touch, Fitsync might be just what you're looking for. This Web application will track and organize exercises, help you put together a solid workout, and log results with a tap or two.
Included are a slew of exercises you can browse through and stack together. There are also recommended workouts you can borrow from others. The application makes use of the iPhone's video-playing capabilities to provide demos of each exercise so you'll know what to do. Most of these are only a few seconds, so they'll load pretty fast, even on first-generation iPhones on a weak signal (which can be typical in most concrete-laden gyms).
As the name would suggest, Fitsync's iPhone app will sync up workout data from your phone to your Fitsync.com account. You can the see how far you're progressing with each muscle group or particular exercise, and even get recommendations for other exercises based on what you've done in the past.
Fitsync is free to try out for 15 days. After that, you've got to upgrade to the $4.95 monthly plan to retain access to the mobile version, though you'll still be able to enter your workout data through the less iPhone-friendly desktop iteration.