Open Source projects are a great way to build experience
I suggest you look for an open source project. There's hundreds of them - SourceForge and Github are hosting sites for open source projects aplenty. With version control systems like Mercurial or SVN, once you've got an account, you can start contributing, and the system will keep track of your changes.
There are also large projects like Mozilla and LibreOffice, with plenty of people to help you along.