Here's a pretty compact graphical presentation of the basic chords. This site also has a lot of other good information.
http://www.apassion4jazz.net/jazz_chords.html Bob Frazier has a good website with the theory of chord spelling summarized nicely.
http://catalog.com/sft/bobf/music_theory.html Ralph Patt has listed over 100 common chord progressions and bridges found in over 400 popular jazz songs.
http://www.ralphpatt.com/Tonal.html Ricky Adams' Music Theory site has a series of good on-demand lessons available. Its a good site.
http://www.musictheory.net./ Duane Shin sells lesson videos, but also has some very good illustrated chord information available free from this index page on his web site.
http://psrtutorial.com/Resources/R_ChordSecrets/r_chordsecrets.html England's Dr. Bryan Blood's explanations are also clear and helpful.
http://www.dolmetsch.com/theoryintro.htm Here's another "chord analyzer" similar to the PW link posted earlier, but with a little different format.
http://guitar.to/piano/index.html Finally for something a little bit different, try
http://members.aol.com/chordmaps/chartmaps.htm which attempts to "map out" possible chord progressions in a kind of "chutes and ladders" style. It misses some progressions, I think, but it has a different perspective that may be of help to you, at least a little later on.
All these people are saying basically the same thing, but it often helps in understanding something to come at it from several different angles.
Good luck,
bob