I can see the light at the end of the tunnel, Cat is quickly reaching a stable 1.0 release.
Version 0.9 of Cat is now available online at http://www.cat-language.com. Cat now passes over a hundred tests, many of them designed to thrash the type inference engine thoroughly. Thanks to Sandro Magi, Cat is now also supported on Mono 1.13.8.
I am currently working on more complete, and up to date version of the documentation, though I have recently updated the syntax description.