You just need to go to the website and click "plan a cruise", then "Search for a cruise", then click the Cruise calendar and then change the year to 09. There are lots to choose from. My husband and I are looking at the Mariner for June of 09 leaving from Los Angeles.
Most of the ships for ALL cruise lines leave the Caribbean for other locations in the summer. However, since we have recently researched extensively (my son's graduation present for June 2009) I can tell you that RCCL has Explorer of the Seas (9 day) out of New Jersey; Monarch of the Seas (9 days) out of Norfolk, Virginia (I think)...Princess has a 9 day cruise on Caribbean Princess out of NY...NCL has one or two available as well, but I didn't research them well. Celebrity had no Caribbean cruises in summer of 2009 that I could find.
I could not find any (Caribbean) cruise leaving out of Galveston or even Miami in the summer months. I did not research any cruises shorter than 7 days, however.
You'll find the cruises popping up on the websites right about now for June 2009. And, you can look at summer of 2008 to get an idea of what they will probably offer throughout the summer of 2009 if they haven't released information yet.
The 9-day cruise itinerary was interesting on both RCCL and Princess, especially if you enjoy days at sea (which we do).