I recently stumbled across Gibson's Skills House site. They have a couple dozen really cool lessons to help tighten up your playing.  And of course, they are free. The lessons are grouped into categories:

• Foundation Lessons
• Style Lessons
• Power Workouts
• Interviews
• Guitar Apprentice (featuring a Guitar Hero-like interface)
• Song Lessons

The lessons all have high quality video, and supporting documentation like tab. Here is one example of a song lesson, the Kink's You Really Got Me (although the lesson really teaches the Van Halen cover.) Well done, Gibson. What other sorts of free resources are out there that you have seen?