Jazz students at Trinity-Laban are producing useful research into practicing… One in particular, offered online is Dee Byrne’s very useful practice-based research: Learning the Grammar of Jazz
there will be more to follow so watch this space.

Other excellent sites offering professional advice with practice are below:
How To Practice
Inspired Practice
Jazz Heaven
Metronome Exercises in 4/4
MusiciansWay.com
The Musician’s Way Blog
The Practice of Practice
jazzadvice.com