General Lesson Web sites
A really good lesson-oriented site here, that offers lessons on scales, chords, and more. You'll have to become a site member (totally free) in order to get access to most of the lessons.
A rather large archive of guitar lessons, organized by category. Includes some interesting lessons on how to play different styles of music.
A bunch of lessons online, plus great other features, like interviews, a chord generator, photo gallery, hot news, and more.
A wonderful series of lessons, brought to you by Gunharth Randolf, that cover both guitar theory and actual guitar playing. Features an online harmony quiz to test your knowledge.
Guitar Lesson World
A large number of lessons available to those interested. Some lessons are less than thorough in their scope, but they're helpful nonetheless.
Nice site created by Larry Pinkerton, with a series of intermediate to advanced lessons focusing primarily on jazz guitar.
Guitarschool.net Video Lessons
Some really insightful free guitar video lessons, designed for players of all skill levels. If you like these free lessons, you can pay to access many more video lessons.
Guitar Start Lesson Archive
This site offers a bunch of lessons, some of which are excellent, others which are not as impressive. Still, this is a big resource that's worth seeing.
Large archive of scales, lessons, riffs, and more. Visitors are encouraged to submit their own work.
Harmony Central Lesson Archive
Collection of lessons spanning many different topics. Many of the lessons have been submitted by users, so some of the information is less than top quality.
Ultimate Online Guitar Tutor
Well organized, and well-documented lessons aimed at the beginner guitarist. Many lessons include audio clips for clarification.
WholeNote: Online Guitar Community
A great site that lets users create and browse online lessons. Visitors can also create audio tracks right on the site to jam along to.