It might be too late to get an internship at a large company, but there are probably startups and other small companies that would love to have interns.

It doesn't hurt to find companies you're interested in an shoot them an e-mail inquiring about a summer position.

This worked for me when I e-mailed a couple of startups, one of which was Justin.tv. Even though they weren't specifically targeting interns, I e-mailed them anyway, with a solution to their pre-interview programming problem.

Now I'm in San Francisco =).