JavaOne at the Moscone Center is the biggest conference for the Java world. It's one heck of an experience to meet all the world's Java developers and interact with the Java programmers of the world.
This year Sun has put up a page where students and educators can get in free at the conference. The JavaOne 2009 from June 2-5, 2009, Moscone Center, San Francisco, California has a normal entry fee of $1750-$2000 depending on the sessions.
It is a great opportunity for students to meet some of great programmers. Great learning experience and exposure to the Java world.