This looks like it will be excellent for intermediate and beyond players who want to learn about jazz improvisation:
https://class.coursera.org/improvisation-003/class
This is not a series of video lessons to take at your leisure. This is a 5 week structured on-line course by a Berklee School of Music professor with weekly assignments that will be reviewed by your fellow students.
The course started today, October 14, 2013. If you are interested, register and get started with the class now.
Free Jazz Improvisation on-line course
No explicit, hateful, or hurtful language. Nothing illegal.