My advice for Venice if you arrive by car:
Park in either Treporti or Punta Sabbioni and take the ferry to Venice, stop along the way in Murano and Burano for lunch! High quality hotels are dirt cheap on Lido around Oktober till November. I stayed at a 4 Star hotel that usually charged up to 650 Euros per night for only 85 Euros (double bed, including breakfast).
A few things from Wikepedia about Venice:
Venice is a city in northern Italy, the capital of the region Veneto, with a population of 271,367 (census estimate 1 January 2004). Together with Padua, the city is included in the Padua-Venice Metropolitan Area (population 1,600,000). The city historically was the capital of an independent nation. Venice has been known as the “La Dominante”, “Serenissima”, “Queen of the Adriatic”, “City of Water”, “City of Bridges”, “City of Canals” and “The Amsterdam of the South”. Luigi Barzini, writing in The New York Times, described it as “undoubtedly the most beautiful city built by man”. Venice has also been described by the Times Online as being one of Europe’s most romantic cities.
The city stretches across 117 small islands in the marshy Venetian Lagoon along the Adriatic Sea in northeast Italy. The saltwater lagoon stretches along the shoreline between the mouths of the Po (south) and the Piave (north) Rivers. The population estimate of 272,000 inhabitants includes the population of the whole Comune of Venezia; around 60,000[3] in the historic city of Venice (Centro storico); 176,000 in Terraferma (the Mainland), mostly in the large frazione of Mestre and Marghera; and 31,000 live on other islands in the lagoon.