Hi Pat
We visited Venice in August 2006 and stayed at Camping Cavallino on the Jesolo Peninsula. This peninsula has a line of excellent campsites stretching along the beach which faces the Adriatic - Alan Rogers Italy (2009) lists over 20.
Here is the review I wrote at the time which includes a a number of tips about geting the best from visiting Venice:
http://www.ukcampsite.co.uk/sites/reviews.asp?revid=7387
I would highly recommend Camping Cavallino. We had not booked but just phoned ahead the day before we arrived. It was an excellent base both as a beach holiday centre and for visiting Venice. We were given a large pitch near to the beach. We, also, visited Camping Union Lido nearby to attend the English Church Service - that campsite has a full-sized Church building. Union Lido is HUGE Alan Rogers Italy (2009) says that it has 2600 tourer pitches. Whilst not our "cup of tea" it was VERY impressive and its facilities included a very large supermarket, a shopping precinct, hotel, several swimming pool complexes and a sporting complex and camping superstore on the opposite side of the main road.
The only downside if you stay on the Jesolo Peninsula in high summer is to avoid the main road on Saturday as it tends to be on a Saturday as holiday traffic arriving and departing turns it into one long traffic jam. It is possible to avoid the traffic by using the side roads.
Post again if you have any other questions about Venice and the surrounding campsites.
Tim