There are a huge number of web sites with good information about guitars, guitar music and lessons. Here are some of the more useful ones for those beginning to study playing the guitar.  First, a chord generator by Jim Cranwell.
Picking up tunes by ear at Jam Sessions *

Beginner Strum Patterns from About.com - Very clear directions with sound files. Includes links to many other guitar lessons and resources.

Many clearly explained lessons from Acousticguitar.com.

Cyberfret.com has very useful lessons on chords, strumming and more. It includes videos, charts and more.

The lessons available from guitarists.net are also well done and some are available in printable format.

More useful lessons are found at guitar site.com . There are lots of resources here. Like some of the above sites, they explain the theory behind chord structures and playing.