Oh, I thought of one the other day. You know you are a bike geek when you can answer average speed, how long it will take to get to point a, and how long will it take to catch someone and you never could before.
Also you know off the top of your head these numbers
6min mile is 10mph
5min mile is 12mph
4min mile is 13mph
3min mile is 20mph
2min mile is 30mph

And the real geeks know the 30 and 15 second incrment averages.