Garmin Edge 305

Last year, my big birthday present was a Garmin Edge 305 with heart rate monitor and cadence sensor. Since July, I have logged 2294 miles with it and have loved it.
Basically, the 305 is a cycle computer that measures speed, distance, and elevation by using GPS. It also records your rides as GPS tracks that can then be uploaded to Google Earth (see Google Earth and GPS Babel posts). If you purchase the optional heart rate monitor and cadence sensor (like I did), you can also measure heart rate, cadence, and continue to get accurate speed and distance readings if you lose GPS reception (ie. during indoor training).
When you return from your ride, you can upload the ride data to Garmin Training Center, using a standard mini-USB cable, and get the full statistics of your ride including: GPS map, distance, time, speed (ave, max, instantaneous), ascent, descent, laps, pace, calories, heart rate, and cadence, as well as weekly totals, and overall totals.
The 305 will also let you save rides as "courses". Once you have saved the ride as a course, you can then race your previous time (with instantaneous information as to how far ahead or behind you are) or e-mail it to a friend and let them race it.
Another thing that the 305 will do, which I have not tried so far, is creating workouts and letting the 305 walk you through them (with set heart rate ranges, times, alarms, etc).
I have only had one difficulty with the 305, and that was that it would not power on once, but I called Garmin (they are really helpful), and then showed me how to soft reset it (press and hold "lap" and "mode" for 5 seconds).
The only thing that the 305 lacks is the ability to measure power, which was recently remedied by the release of the Garmin Edge 705. The 705 includes all of the functionality of the 305 and adds a color screen, wireless power option (purchased separately), and the ability to get turn-by-turn directions (with optional maps). I want one!
My suggestion for buying a Garmin Edge is Amazon (I was able to get mine with heart rate and cadence for $275 instead of the suggested $433).