I'm not sure how much releases matter as most everyone seems to be working off of the git branch and we tend to not have to do a lot of fixing of past versions.
Anyway, I've tagged and uploaded tar balls for the latest version of Ansible, 0.5, codenamed "Amsterdam"
https://github.com/ansible/ansible/downloads
0.6 now corresponds to the development branch, "Cabo".
Changelogs are here: https://github.com/ansible/ansible/blob/devel/CHANGELOG.md
(Most notably, --connection=ssh allowing for all sorts of fancy stuff, as mentioned previously on this list, including Kerberos support, jump hosts, and so forth. Rock!)
Various items from the change log will be added to the doc site shortly.
0.6 doesn't really have any major plans -- there may be some tuning that happens around performance (I know this file doesn't need to be copied, what to do with very large play groups, etc). Some folks have been improving the modules recently, which is always good to see. I am glad we decided to go with a small core and are keeping them well up to date. Let's consider this summer vacation as we continue to take pull requests for ideas that come up along the way. There's no major refactoring or anything in the pipe, so it should be a nice time to kick back.
(Previously I threw around some ideas about data access to ansible facts, though that didn't seem to be very interesting to a lot of folks, so I'm probably not going to do it.)
--Michael