Aside from having access to all the Java web frameworks, Clojure has Compojure and Conjure on the higher level and Ring (equivalent to Python's WSGI and Ruby's Rack) for lower level.

I wouldn't discount Clojure as not ready for complicated web applications based on it's young age; Java servlets can be written in Clojure. Not that Java servlets are great, but they are widely used for non-trivial web sites.

Clojure is great at removing the ugliness of some Java APIs, I recall that Compojure is built atop servlets.