The Sourceforge page for Clojure currently lists the September 16, 2008 version as the latest release for download. Unfortunately, a lot has changed in Clojure since then. For example, the syntax for java interop has changed so that a lot of older Clojure code won’t work anymore, and if you’re running the September 16 version, newer code won’t work either: this includes examples from the latest release of Stu Halloway’s Programming Clojure.
Everyone is downloading the source via subversion and building their JARs. This is the de facto latest release. I would advise you to do the same. Here are a few ways to make sure your Clojure is up to date (Thanks to Philip Fominykh, Keith Bennett, and Craig Andera for the help.)
The most straightforward way is installing directly from source (wikibooks).
A more comprehensive solution is offered by Bill Clementson: an organized directory setup with build commands and Emacs/SLIME support. (Aquamacs users, add his ~/.emacs code to your Preferences.el file.)