Okay, I've decided to put the free jazz links I promised Polly in this thread, just because I can't think of a better thread to put them in. We were derailing some other thread with this discussion, so at least now it can continue in a semi-relevant thread.
Polly, I was trying to find you some good links to the European collective improvisation, only to discover there are precious few clips online. The FMP label (I recommend you read about it here: http://www.fmp-label.de/index_en.php
or via Google search) had an impressive artist stable of both European and American artists. I wanted to start you out with Peter Kowald's excellent Was Da Ist, but I can't find anything online.
Here's something from Alexander von Schlippenbach, the pianist. http://youtu.be/Kv7nls6ur9k
And a version of Take The A Train by Matthew Shipp: http://youtu.be/HfZmJSVAPQY
Okay, are you feeling nervy? When you are, let's see if you're ready for this classic. The slightly terrifying Machine Gun by Peter Brötzmann