Prominent open source Clojure projects:
- Compojure - a web framework (since you mentioned Spring)
- Ring - HTTP abstraction API
- Incanter - R-like statistical computing and graphics environment
- Leiningen - a build tool for Clojure
- Clojure-Contrib - you mentioned the core library, but contrib is definitely worth looking at as well.
- Enclojure - Clojure IDE tools (used with Netbeans/Redcar)
- Counterclockwise - Eclipse plugin for Clojure
- 4Clojure - Website with interactive fill-in-the-blank Clojure problems
A few blog posts explaining bite-sized Clojure applications:
- Pong in Clojure
- Buddhabrot in Clojure
