Well... where do I start? I've come across plenty of sites that look useful at first, as I've been scouring the internet
but I haven't gone through any of them in great detail (because I don't have my guitar D: ) but I'll send you a few.
www.ultimate-guitar.com - Great for tabs, if you just want to be able to play a particular song. I think you can tell if a song is too hard for you because your progress will be *really* slow. There are also lessons on here about how to do various things with the guitar that look really informative, but you may find that you learn better from instructional videos like
this, like Max. Justin also has a website that Ali recommended to me:
www.justinguitar.comhttp://www.cyberfret.com/theory/index.php - This looked useful when I first found it because it explains scales and chords (and presumably arpeggios), and if you can learn these you can work out different songs (kind of like when I'm playing the bass and I make a mistake then it sounds like a song I know, then I work out the rest lol)
http://www.chordbook.com/guitarchords.php - Might come in handy, if you don't have a proper chord book, or if you just want to learn some chords (I'd start with a few major and minor)
http://guitar.about.com/ - I've seen this recommended on here before, and it seems to cover all the basics
http://www.jemsite.com/blog/learn-guitar-songs-faster/ - I liked the tips on this site
http://shredguitarschool.com/ - This website made me lol, but I haven't looked at any of the content. It may or may not be useful to you.
http://www.ehow.co.uk/guitar-progressions/ - I don't even know what progressions are, but I was watching this black guy played the bass and he kept talking about chord progressions, so I guess they're important.
Tips
If you're trying to learn a specific song, and you're having trouble working out where to put your fingers, it might help to watch a cover because it will give you ideas.
You might want to read up on different tunings, because a downtuned string can make things easier (e.g. some RATM and A7x songs I've tried use Drop D), and some bands use an entirely different tuning like Drop C (which is D tuning [e.g.
Extreme Unction] with a downtuned bottom (deepest) string [e.g.
Disturbed, any song by The Faceless]). Some forums I've seen like to slag people off for trying out different tunings before they know all the theory and stuff for standard tuning, but haters gonna hate
The bass website I've been using keeps saying 'Don't become a slave to tabs' - it's better if you know the notes you're playing (you can learn the notes of the frets quite easily) but I cbb to do that really. I'll work it out if I need to.
That's everything I can think of!