Some time ago I found about mvnrepository.com and I must say this is something I've been waiting for a long time...
Through its RSS feed I am aware of any updated library that goes on in the maven world. I am not sure which repositories are available through its interface though, if you have more information on this please let me know.
The best feature is the search option, looking for libraries has never been easier. Including a new library in your pom.xml is just a copy paste away! If you are a Firefox user then make sure you add this link to your bookmarks, setup a nice keyword -- mvn for example. Then any library is just at your finger tips using mvn [your search] in your Firefox location bar.
This is really great stuff...