As a teacher, I have found this book to be one of the best. It's a Real Book with over 40 great tunes. On the left-hand page you get the tune with chord symbols, like any Real Book, but on the right-hand page you get Supplemental Material:
Sample 3-note piano voicings, first with a Root note, then rootless. This great for transfering to the guitar: a good exercise for guitar students. I have the Bass-clef version, but I believe the C-clef version also has guitar chord boxes.
Useful Scales - based on the chords in the tune.
Sample bass line - great for playing on the guitar while grabbing a few 3rds and 7ths above.
Not directly for guitarists, but highly recommended for all guitar students. This is Level 1:
The Real Easy Book Level 1 (Sher Music Co, 2003) C edition @ Jazzwise.com
Does anyone else here use it?