This page contains historical information (it was accurate as of December 2015). For the up-to-date list of Contrib Libraries, see the API page on clojure.org.
Modular Contrib projects (compatible with Clojure 1.2.0** thru 1.5.0, each in its own repo). **Mostly... support for Clojure 1.2.x is being dropped from several Contrib projects now - check the individual projects' test matrix on the build server to be sure of version support.
Monolithic Contrib (1.2 and earlier. Improvements to any code here will begin with promotion into modular contrib.)
If you currently depend on the "Monolithic Contrib", you are encouraged to look at the new modular contrib projects to see if your dependency could be replaced by specific modular dependencies, as this will make your transition to Clojure 1.3 and beyond easier (certain parts of the "Monolithic Contrib" are no longer compatible with Clojure 1.3 and beyond). This is particularly true if you maintain a third party / community library project, so that developers who are already using Clojure 1.3 or later can then use your project. Please read this contrib library migration guide - a work-in-progress!
If you can't yet switch to the Modular Contrib but you want to migrate to Clojure 1.3 or later, you might want to look at Allen Rohner's unofficial version of Contrib 1.2 compiled against Clojure 1.3 to get you started.