I don't like blogs with dozens of links to other related websites or so-called "friend blogs", but I have added a couple of links to this blog (you can see them on the right) that I considered very interesting:
Casa Valdez Studios: an incredible blog written by David Valdez, with plenty of ideas and materials about jazz. A must read.
The Zone: By pianist Jessica Williams. This woman shows such a profound love for jazz that reading her entries teaches you as much about jazz as listening to Miles or Parker. And you can download some (many) full-length mp3s from her website!