Just thought I'd mention that you might want to make use of the Jam feature on each page too. Not all instructors post jam tracks to go along with their lessons but I'm making a concerted effort to try and include an example song with each lesson showing how the chords are played and strumming methods used. Each lesson has an MP3 file and a looped Jam track that you can practice to.

For instance if you were interested in learning seventh chords you could find 14 lessons here:

http://guitartricks.com/lesson.php?input=9609&s_id=181