The two programs I have found best for learning the guitar:
I've actually used both myself, and my playing has improved a lot!

Guitar Tips Online Learn from the best! This guy is amazing, he's got heaps of tips and helps you out with all you need! Guitar Tips

Guitar Songs Unleashed Know the basics? Now learn how to play your favourite songs with tabs, audio and video! Guitar Songs

Basics

"How to read tabs, and begin playing the songs you have always wanted"
"Tablature notation, what those letters etc. means"
"Choosing a guitar that suits you the best!"
"What Are The Different Types Of Guitar Strings Available Today?"

Scales

The Pentatonic Scale

Killer Riffs!

These "lessons" shows you how to play some legendary riffs
And they're made by me.

#1: Deep Purple - Smoke On The Water (Beginner)
#2: Metallica - Enter Sandman (Beginner)
#3: Black Sabbath - Paranoid (Beginner)
#4: Europe - Final Countdown (Beginner/Intermediate)
#5: Nirvana - Smells Like Teen Spirit (Beginner)