Not everyone knows it, but open source plays an enormous role at Google. Each time you use the Google search engine, you’re using open source software. Google relies on the Linux kernel, GCC, python and Samba and commits code into each of those projects.
So if you are interested you can read the terms of service first to be sure that you are eligible to participate, then you can choose from one of the mentoring organizations participating in Google Summer of Code 2007 : Coppermine, Dojo, Creative Commons, Drupal, Django, Gallery, Joomla, Moodle, Mozilla, MySQL, PHP, PostgreSQL, SquirrelMail, Apache, Wikimedia, WordPress, … etc. Organization application are closed now, and if you are interested check project ideas from different organization depending on your skills and submit your participation. One of the very interesting open source events sponsored by Google, which supported 1,000 students with over 100 open source projects until today to create hundreds of thousands of lines of code. The good news that this year the project will accept an additional 200 students beside some additional open source organizations.