Google is once again sponsoring grants of $4,500 for students to work on open source software. Applications are only accepted between May 1st and May 8th 5:00PM PDT. The google summer of code site http://code.google.com/summerofcode.html is returning a 502 error code right now, possibly due to that deadline and the number of people who are interested.

Projects that qualify for these grants includes one of my favorite tools NMAP.
From: http://www.insecure.org/nmap/GoogleGrants.html
"The 2005 Google Summer of Code project was a tremendous success (project results) and benefit to the Nmap Project, so we are delighted to announce that we are participate again for their 2006 program! This innovative and extraordinarily generous program provides $4,500 stipends to hundreds of university students to create or enhance open source software during their summer break!"

Update the google summer of code site is being responsive again.
You can find a complete list of the Mentoring Organizations here now.
http://code.google.com/summerofcode.html