If you're into mitten crabs, caulerpa and colonial tunicates, you'll want to check out the Fifth International Conference on Marine Bioinvasions, to be held at MIT this May 21-24. Judging by the 2003 and 2005 versions, the conference is likely to be very well-attended. Unfortunately, it is also going to be fairly pricey, unless you've got a sponsor ($325, with no daily rate. At least they have a significant student discount: $125!).
Those of you working in the field of marine invasiions should note that the deadline for abstracts has been extended to January 19th. So get going!