Teoria is a more serious site that has various tutorials. Here is the one on reading music:
They also have sound examples, which is a big help. Though their metronome doesn't seem to have a very good rhythmic sense! Or maybe it is just my internet connection.
Here is an online course that includes both reading and music theory:
Here is a blog on music theory:
I'm not making guarantees about these sites as I just took a brief tour of them, but all of these look pretty good.
I'm wondering if perhaps we might be on the verge of a new era in teaching music. Services like Skype might allow students to learn from teachers that are geographically remote. But in the meantime, I have to recommend that you find a real, live teacher. There are free online courses, but most of them put me to sleep!
That is way too 'talky'. I think it is best to just start playing, put the fingers on the guitar, adjust the position. After a bit, show how notes look like written down, etc, etc. But don't load the student down with a bunch of philosophy and precepts that can have no real traction for them yet.
Here are a couple of pretty good teachers in action:
Despite the guitar's Spanish heritage, English is the international language of guitar masterclasses--even in Spain!