About a month ago I joined the Delcamp Classical Guitar Forum, and so far I've found it amazing. This one is the Forum in English, though there are also sites in French, Italian and Spanish.
There are a lot of people participating (composers, guitar players, luthiers), the conversations are very well kept to the subject (with well organized topics), and the people are really helpful and friendly.
And the resources are also very good. In it you can find information about technique, many recordings of common repertoire pieces, plenty of music scores, etc.
All in all, this is by far the best place in the Internet for sharing guitar experiences with other musicians. If you happen to stumble here and have any interest in Classical Guitar, make sure you visit the Delcamp Forum.
Thanks Jean-François Delcamp for starting this out!