The Django 1.4 beta release is now available for testing.
Although the 1.4 beta can be downloaded as a package, it's probably best to get it from the SVN development branch (also mirrored on github) so you can update and take advantage of bug fixes as they are incorporated into the code base.
For more information on the new features coming in 1.4, come see my talk on Tuesday night's Django District meetup in DC.