I have not heard of any, but if you discover one, I'd be interested because I'm in the same boat (no pun intended). My wife and I have discussed this but we keep running into the issue of where the doggies would be doing there business and then realize that there probably are customs issues with bringing animals in and out of the country. I think the issues involved in such a cruise prevent the cruise lines from offering one.
Luckily we have great friends who come and take care of our pets when we go out of town.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007