Hey Jarrod, Tina and I went for 3 week to Italy a few months ago. In Venice, we stayed at The Hotel Riviera on the island of Lido. Its just across the water from the Grand Canal entry point. A quick 5 minute water taxi, and your in San Marcos Square. For the money, (or saving of money) Lido wasan easy choice. Plus only about a third as crowded.
In Rome, we stayed at the Nord Nuova Roma. Its pretty centrally located, and you can walk to anyplace from there. Coliseum is about a 20 minute walk, Pantheon, Trevi fountain, and the Vatican can all be walked to, or take the On/Off Red Bus. Let me know if you want any info on Florence or any other side trip towns (Pisa, Oriento, etc)