There is a free iphone/droid app (also works with any GPS) called Strava that is becoming more popular around here.
Basically, it has some rides around the city mapped out, including a lap around hefner, a lap around overholser, a lap around draper, etc.
You ride with your gps or phone in your pocket with that app going and as soon as you roll past the starting line the timer starts. When you roll past the finish line the timer stops.
You can upload your ride and it will show you a leaderboard with other riders so you can see where you stack up. You can also create your own routes and it will notify you every time you set a new PR.
It's a pretty cool idea, but it will get even better if more people start using it and there is some friendly competition/banter going back and forth.
You can also use it for running, but right now it looks like there are only a few people with mapped out run courses. Check it out in the app store or at strava.com