Allguitarchords.com has some great tools for learning guitar.

You can make your own chord progressions and scales with the use of an interactive fretboard. It also has a glossary of common terms and a tuner.

Perhaps the best part of the site is the Jam tool, which gives a visual of a chord on the interactive fretboard and also displays the chord in tab form. You can then play a midi files which shows you what the chord sounds like!

There is a list of a few dozen popular songs where you can click on the chord you are trying to play and it will display the chord in different positions on the fretboard. I found this a very good tool for quickly remembering different finger positions for alternative chord positions.

Visit site: http://www.all-guitar-chords.com/

Levels: Beginner, Intermediate, Advanced

Other Resources:
1. Forum
2. Guitar Jam Machine (interactive chord finder)
3. Metronome
4. Tuner