This interactive guitar is kind of nice to visualize the fretboard and some arpeggios.
Here is another fretboard which shows the intervals of scales.
I've been adding flash card sets to this site to quiz myself.
So far, I have flash cards for these topics:
- Relative Majors and Minor keys
- Major Triads
- Major and Minor Triads
- The 2-5-1 Chord Progressions (which also help you learn the cycle of 4ths)