And Dream Theater (and Liquid Tension Experiment): http://www.dreamtheater.net/media_tabs.php
However, they are publishing the songs made by themselves. The problem here (GN) is many song (all?) used as lessons have copyright and that is very much stuff, it is a lot of work!
On the other hand, not all the songs are equally interesting for visitors. Usually you want to learn (with) songs that you know. I mean, I prefer to learn to play a Beatles song than a, for example, Buck Dharma song, basically because I never heard about the band, others will say the same about Veloso, etc.