I mentioned this on another submission but Christophe Grand's Moustache routing library, http://github.com/cgrand/moustache, is great in conjunction with Ring. It makes very idiomatic use of destructuring to define routes, for example you can do stuff like the following:
(def admin-post
(app [""] "admin post index" ; /admin/post/ or /admin/post
["new"] {:get new-post ; GET /admin/post/new
:post save-post} ; POST /admin/post/new
["edit" id] {:get edit-post})) ; GET /admin/post/edit/:id
(def admin
(app [""] "admin index" ; /admin/ or /admin
["post" &] admin-post
["posts"] {:get all-posts} ; /admin/posts
["settings"] {:get settings})) ; /admin/settings
(def main
(app [""] "index page" ; /
["post" slug] {:get get-post} ; /post/:slug
["admin" &] admin))
Ring is a lower-level library than Compojure. It provides a variety of common web-related utilities that will be needed by many Clojure web developers, regardless of what higher-level libraries they choose to use. The purpose of Ring is to prevent those utilities from being rewritten all over the place while also allowing custom utilities to be shared among Clojure web developers.
Note that Compojure 0.4 depends on Ring, to which it delegates things like parameter parsing and cookie manipulation.
If you're familiar with the Ruby web ecosystem: Ring : Compojure :: Rack : Sinatra.
Ring is an underlying piece of compojure, though as compojure moves towards 0.4 where weavejester is breaking a lot more of it up into libraries the difference goes down, since you'll be able to take the parts you want and not the ones you don't, so you could use ring for middleware/routes/etc and take his html library that used to be built into compojure and take that instead.
