We are a bit north of you (Montreal) but always looking for strong interns: http://bit.ly/eCb7FU

I would echo the comments about www.youtern.com and www.internmatch.com though. We get about 1/3 of our intern applications from these websites (the rest comes from direct referals and on-campus recruiting).

Finally, don't underestimate the value knocking on doors. I have hired a bunch of great interns and employees over the years who just "showed up" and pitched themselves into the organisation.