I've been learning how to maintain bikes for about a year now. Here's a quick list of the sites and books I've used. Good luck yourself!
- Art of Road Bike Maintenance and Art of Mountain Bike Maintenance. It is not as complete in the details, but gives you a good overview.
- Sheldon Brown. This is the next level down. Sheldon's articles are just great and he's very practical. Helped me find great things like rear derailleur self-shifting solutions. Also good advice on routing cables and also on motorbike style brakes (you wire the right hand to the front instead of the rear brake).
- Lickton's, but I try to direct my business here as much as I can to support their great efforts.
- RoadBikeRider.com. I haven't used this site much but it appears to have some very good advice.