As a relative new-comer to the cycling world I've been spending the last couple of years learning all about how the bits of a bike work and what needs changing, cleaning or testing when. A very handy site, Made Good is full of helpful videos to guide you through a lot of the tweaks, checks and servicing bits you need to do on your bike. Presented in a very clear, and more importantly, non condescending way the videos guide you through the full spectrum of bike maintenance And with a whole load of new videos due to be released soon you could find the answer to your biking problems without having to leave the house. So no need to be talked down too but a guy in the bike shop.
There is also a really good magazine section featuring a blog and forum, so if your particular problem isn't solved straight away you might get your answer from of the sites users. There's even a piece from someone you might know of.