I stumbled across a great website by a bass instructor but it is useful for all stringed players. I hope it is OK with the Cafe to post links but here it is:
It has alot of good resources and applies to the mandolin just fine.
The tool I found most useful is a fretboard scale generator that generates a graphic showing note positions for every key and for dozens of scales and chord notes for most stringed instruments in many different tunings. It is under:
I'm trying to learn D Minor Swing and was looking for some minor scales. This helped. I know I should be able to figure it out (flatten the third) but this was faster. I'm a visual learner so graphics help too.
Usual disclaimer, I have no connection with that site, commercial or otherwise, I just thought y'all would like it. By the way, the owner of the site is monitoring and responds quickly to his comment page. Seems like a good egg.