This post is a compilation of URL's to ten different blender model and rigs which are available on the internet and appear to the best of my knowledge to be released by their copyright owners under either a Creative Commons license or the Blender Artistic License. I've started to play around with them, and here is at least one way I intend to provide "attribution". I'll leave it as a game to the view to figure which is which.
License: Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.
License: Creative Commons Attribution 2.5 License.
License: Creative Commons Attribution/ShareAlike license
License: See below
URLs: http://www.creationanimation.com/sites/thoenes/freestuff/suzanne-rigged-ver1.blend http://forums.cgsociety.org/archive/index.php/t-277859.html
License: Blender Artistic License
More details are at Elysiun Forums http://www.elysiun.com/forum/viewtopic.php?p=478085#478085
Man in Suit (Armatured);
Man 2 as Doctor (Armatured);
Woman in Casual Clothing (Armatured)
License: Creative Commons Attribution 3.0 License.
Blender Summer of Documentation Walk Cycle
License: I'm not sure
My own very ugly rig. I'm not sure if I've released it or not.