Well...um...it depends on how serious you are about learning the guitar. If you're pretty serious then I'd recommend getting the Guitar Gritmore book of Progressions and Improvisation. That'll teach you about the Circle of Fifths. Just the first 50 pages alone of that book are enough for you to hack at for a while. If not that...well use the resources of the internet. I doubt that every site you go to will be accurate. Try and find a site that's reputable. One place you might want to start is the
Fender Players Club - Guitar Lessons
Fender Player's Club...
That's pretty useful if you want a couple of free tips that have excerpts from various Instructional books and DVD's...
Good Luck man...:icon peac