I've noticed some users asking about music theory. It might be useful to have a thread posting weblinks to some free theory websites around the web.
I've found this one:
http://www.guitarchordsmagic.com/
Maybe people could post some links to other good sites they've found?
Btw, I myself am not really super knowledgable about theory--but I've found some aspects of it useful (for example relative major & minor chords).
—Plus! Other stuff not surf: https://soundcloud.com/jamesmileshq
Enjoy every minute