I ran across this page a while back. Some decent stuff there, and a nice forum (scroll down and click on Jam Session for the forum):
http://www.zentao.com/guitar/theory/
Having said that, unless you're a heckuva lot more disciplined than me (which wouldn't be a tough feat to pull off), I don't think there's any substitute for one-on-one lessons with a good LIVE guitar teacher. I've played sporadically for years, but have progressed immensely in the last year after finding a good local teacher.