This is a great site for guitarists featuring a variety of information. You can go to them for free online lessons, check out their extensive forum, read interviews, reviews, tabs, wiki, or visit their very own shop for t-shirts, mugs, CDs, etc. Truly a great resource. The Rosetta Stone Of Guitar has received a great review from the senior editor of guitarnoise.com, Nick Torres. Click here to read the review yourself and here to read a forum thread on it.
If you haven't seen this one, you realy MUST SEE it! This is sheer comic and flash genius! It's like a really funny interactive movie. You can tune up your guitar as well as learn how to play the wild and crazy riffs by reading the tabs in the practice section.
Here's a great site that I have frequented over the years. I go to this site for the seemingly millions of lessons in their archive. They've been around for many years and have a lot to offer the ever-growing guitarist. Check them out sometime. You can read some of my posts concerning rSoGuitar over there.
This is the home base of the phenomenally skilled guitarist: Jeff Findley. Check him out for his selection of online lessons, his guitar tuner, many more links and articles.