JW Pepper - A great site to check out jazz/concert and pepr band music. Lots of audio clips on here.
Lush Life Music - Listen to many great Club Cougar charts right here!
Joshua Redman - Redman is one of the best tenors on the planet. Lots of great bio info and useful links to other top jazzers.
Herbie Hancock - The man, the legend, the link! :)
Music Theory - Having trouble with your knowledge of music theory? Do a few lessons on this site.
Jamey Aebersold - Jamey's site is the #1 resource for jazz play-a-long books, fakebooks...pretty much all things jazz!