Happy Saturday!  So a fun activity for your free time is to join in working on some sort of open source project.  There are a large number of projects out there that can use a hand.  The place to start is to swing on over to sourceforge.net and search for a project you might be interested in using.  Source Forge is full of projects in all sorts of stages of development and all types of uses. 

Most of the projects will let you get a current version of the source from the CVS and you can make changes.  If you make any useful changes you can generally pass them back on to the group.  Some projects are organised enough that they have specific lists of things that need to be done so you can (and should) follow those lists. 

Happy Coding.