Here's a fun website

n-Track Studio Discussion Forum
1

guitar chords via Flash

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http://www.chordbook.com/

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Nice one!

Another one that is nice like reference site (and you can download the entire site!)
http://www.musictheory.net/

4

Great sites. Thanks for the tips.

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Another that shows chords, scales and modes, and that allows alternate tuning.Chord Builder