You may find the following links useful:-
For the technically minded ...
- Sheldon Brown: for masses of technical information on bicycle technology.
- Bicycle Helmet Safety Institute: An extensive site with masses of detail on just about everything you need to know about cycle helmets and a bit more. If you want to know how complex helmets are, start here!
- The Science of Cycling: for those interested in the fascinating mathematics and science of how a bike actually works. More complicated than you think!