Nice link. Another great thing to know is how chords are made up, and than exploring those shapes on your own. For example, look at the following three chords;

Gmaj7
(G, B, D, F#)

Bmi7
(B, D, F#, A)

Emi7
(E, G, B, D)

One thing you will notice is that these chords all have similar notes in them. Pending you have a good working knowledge of the neck of the guitar, take the time to try and work some of your own shapes on the guitar neck. Once you have found one of these chords, the other two are not far off. These chords are also great substitutes for one another. Try it out!

Again, great link and another great perspective on this concept.