The hottest toy on IronTeam of late is the Garmin Edge 305. It's a pretty wicked bike computer/heart monitor/GPS device. It's about $275 at Amazon.
For runners, the hot item from Garmin is the Forerunner 305, which is more or less the same product but you wear the device on your wrist. It's about $215 at Amazon.
Anyway, I don't actually want either of these. I really don't care about bike stats, kinda takes the fun out of riding a bike. I do have a bike computer, which has ended up being a very expensive clock (not totally true since I do use it for knowing total distance but close enough).
Some people love bike stats and many bike computers are able to hook up to laptops and you can monitor a workout by distance, time, elevation, etc. Pretty comprehensive. Here's an example.