I would suggest trying to find a hotel in Venice on your own rather than staying out of the city. One of the best parts of staying in Venice is being able to walk around the city after all the day tourists leave. It seems like a different city then especially in the areas that are especially crowded during the day (i.e. St Marks, Rialto area, etc.). Also doing a waterbus ride up and down the Grand Canal in the early evening as the sun is setting is another experience you may remember for a lifetime. There are a number of sites where you can find Venice hotels. Here is a great general information site on Venice that has on it a number of links to hotels.
We stayed at a small family run B&B for 3 days after our cruise and felt we could have stayed another week and still not seen everything we wanted to see. My wife says it gives us a great excuse to go back again some day.
The hotel we stayed at which was a real bargin, I felt, at 100 euros a day with breakfast included was the Alloggi Barbaria. Their website is:
It wasn't fancy and wasn't on a canal but it was far enough away from the main tourist areas so we got to sample some of the local flavor of Venice (like shopping in one of little local grocery stores for some soda and wine) but close enough we could get to St Mark's in an easy 15 minute walk.
If you have the time plan on staying at least a couple of days in Venice because there really is a lot to see and do and everything seems to take longer than you would think.
Hope this helps and have a great cruise.
HAL Noordam 3/97 West Carib
Hal Westerdam 12/97 East Carib
HAL Veendam 11/98 East Carib
Hal Zaandam 12/00 South Carib
HAL Veendam 10/01 Panama Canal
RCCL Enchantment 09/02 W.Carib
Costa Atlantica 12/02 E.Carib
HAL Noordam 03/03 S.Carib
Golden Princess 07/03 Med
Celebrity Zenith 12/03 W.Carib
HAL Maasdam 05/04 Canada