The Compiz 0.9 release has been baking for quite a while as it involved the merging of Nomad and Compiz++ (the C++ rewrite of Compiz), the dropping of Compiz Fusion, and many other architectural changes after the future of Compiz was previously called into questions. It's been about fifteen months since the last official release of Compiz, but again Compiz 0.9 is still on the way.
A call for testing has been put out to try out the latest Compiz 0.9 development code. Many bugs have been fixed in recent days and weeks, but now there is interest of testing Compiz 0.9 by the wider community.
You can read the Compiz 0.9 call for testing in this blog post and on the Compiz mailing list.
Compiz 0.9 was originally planned for release before the end of 2009, but that clearly didn't work out. However, as for a new time-line, "Hopefully a PPA for Ubuntu will be coming soon, and we might even see Compiz 0.9.2~ in Ubuntu Maverick Meerkat if we’re lucky :)" Ubuntu 10.10 "Maverick Meerkat" is due out in October.