Is there a simple way to find out what versions of dependencies are available using Leiningen?
E.g., if I have a web app which depends on Hiccup and Compojure, how can I be sure that I'm on the latest version of each without going to the github page for each?
NOTE: I use Ant and Ivy for building my Java projects, so I have limited knowledge of Maven - so please spell out (or provide Fine Links for me to read) any Maven concepts that Leiningen exposes to me which would help with this (I know that under the hood, Leiningen uses Maven for dependency resolution). Ta.
The Clojure ecosystem has evolved since the original answer was offered. At the present time, I would recommend using lein-ancient:
Its precursor, lein-outdated, has this helpful message in its README: "lein-outdated is outdated". :)
Web service that provides this info, along with badges for readmes.
http://clj-deps.herokuapp.com
Disclaimer, by me.
You should have a look at the answer to this question. Leiningen uses the same versioning mechanism as maven so, for example, if you want to use the latest version of a given library, you can substitute the word "LATEST" for the version number. You can also specify a release version or a version range. Again, look at the answer at that link.
The canonical way of doing this, at least for dependencies kept in clojars, is the lein-search plugin.
Update: See the highest-rated answer below for a more up-to-date response.