one of the reasons I like maven2

http://www.javaworld.com/javaworld/jw-12-2005/jw-1205-maven-p2.html

Suppose you want to use Hibernate in your project. You would simply add a new dependency to the dependencies section in pom.xml, as follows:

   
      hibernate
      hibernate
      3.0.3
      compile
   

And that's it! You don't have to hunt around to know in which other JARs (and in which versions) you need to run Hibernate 3.0.3; Maven will do it for you!

That is sweet, and relieves great pain in larger projects with many tendrils to OSS jars.