Royal Caribbean

Royal Caribbean's Mariner of the Seas will be porting in Galveston starting November 11, 2011 - April 15, 2012. 
April 22 she leaves for the Mediterranean.

Royal Caribbean's Voyager of the Seas will be porting in New Orleans starting November 12, 2011 - April 7, 2012 

Carnival

Beginning November 14, 2011, Carnival Cruise Lines' newest ship, the Carnival Magic, will be calling Galveston home.  Additionally, the Carnival Triumph will reposition from New Orleans to Galveston to operate year-round four- and five-day Caribbean cruises from that port beginning October 6, 2011. 

In turn, the Carnival Conquest and Carnival Ecstasy, both of which are currently based in Galveston, will reposition to New Orleans to operate year-round departures from that port, returning the line to pre-Katrina capacity levels there.

Disney

Disney Magic will be in Galveston Texas starting
August 22, 2012 - December 29, 2012.  She will return back to Port Canaveral Florida for alternating itineraries of the Eastern Caribbean and the Bahamas

Princess

Crown Princess will be porting in Galveston starting December 22, 2012 - April 27, 2013