Christine, regarding the hotel I used in Venice, it is the Hotel Doni. It's on a quiet side canal, between the churches of San Zaccaria and San Marco, and maybe a five minute walk to San Marco. I like it, and have stayed there twice. It's a very central location, but is also very quiet. HOWEVER, It depends on what you're looking for. It's definitely a budget option. It is a very old, creaky building, and the breakfast is fairly minimal. I found everything to be clean. The bathroom in my en suite room was very new; those for rooms that shared a bathroom were older, and I believe that people on the third floor had to come to the second floor to use the bathroom. The owner is very nice, took my bag up the stairs, and really helped me when someone stole a credit card while I was out (for example, he loaned me his cell phone when customer service for Capital One kept refusing my call, because it was from a US phone number). And the night clerk was very accommodating about getting up before 3 AM to let me out on my last day; he was up before I was downstairs.
The other place I've stayed is the convent of the catechumeni. Sorry, I don't have their email, but you should be able to find it on the web. It was about two-thirds of the cost of the Hotel Doni. It's in Dosadoro, across from San Marco, and about 100 yards from the Salute church. No English is spoken, but the sisters were very accommodating when I needed help with something. They take in students during the academic year, and also have a preschool on site.
Finally, both of these places are very simple. No TV, no phone in the room, no radio, etc. And be sure to specify an en suite room if that's important to you.
