I got an email today from Online Guitar Books asking me to post a link or an article. I’m pretty wary of spam, so I put my browser in stealth mode, and went to the site to check it out. It’s legit. Not only is it legit, I came away pretty impressed with the wealth of information on learning and playing guitar. Of course, being curious about modes, I dove into the modes article, which is VERY long and involved. If you’re really after the theory behind modes and practical application of them, then this article covers pretty much all the bases. Be forewarned though, because while the author has a non-formal tone in explaining modes, he takes a very academic approach to them, and it’s A LOT of material. He even admits at the beginning of the article that he went “overboard.” My advice if you use this article is to read it in chunks; practice what you learn in each chunk, then continue on to the next. As with any academic subject, learning is iterative.
So you might be saying, “Oh no! Not another guitar book marketing site!” Yeah, that’s exactly what I was thinking when I first read the email. But this site is different in that instead of giving you a little information, then saying something to the effect of: For more information on this subject, click here to buy the book! The articles they provide are complete lessons. They don’t even have their storefront up yet, but the information they are providing is complete and thorough! So yeah, I’m kind of endorsing it as a good source for guitar lessons.
Anyway, don’t just take me at my word, check it out for yourself!
Guitar Gear 
You’re right, it’s a good site, some good articles. It’s a shame they haven’t got the store online yet, it should do well.
You’re right again about the modes article, it’s thorough and interesting but a bit on the heavy side.
If you’re interested in major scales and modes, I’ve just finished a software program you might like to have a look at.
It only works on the PC so it’s no use to you if you’re a MAC user but you can enjoy the screenshots anyway. Let me know if you want me to post a link to it.