I took a really cool course on bike derailleurs at REI. The instructors taught us how to adjust our gearing, how to keep the derailleur system clean and how to change a broken chain. I found it really enjoyable to get my hands dirty and put all of the different bike parts together. Maybe I should switch my career from lawyer to bike mechanic? It would be a huuuuuge pay cut, but, at least I might enjoy my work and actually have some friends at work for a change.