Tidal is a mini-language embedded in Haskell, for the live coding of pattern.
For community support and discussion, join the tidal forum: http://lurk.org/groups/tidal/
Documentation, examples, demos and tutorials
Installation instructions and documentation is on the new website here: http://tidal.lurk.org/.
For some tech demo videos showing some aspects of Tidal, have a look at this blog post.
Mike Hodnick has a great tutorial on breakbeat slicing with Tidal.
Making programming languages to dance to: live coding with Tidal is the most recent academic paper about Tidal, superseding earlier ones.
The sourcecode is available under the GNU Public License version 3 (or later) on github.