We've been to Venice 4 times, and 3 of those times, we stayed at Al Campaniel B&B
http://alcampaniel.tripod.com/
It's in a great location - just a minute from the San Toma Vaporetto stop, hubby and I had the room with the bathroom across the hall (standard double). We've been mid-Sept and prices were about 75-80 euro. Marco was a great proprietor and we had some great chats with him and other couples when having breakfast (especially an Aussie couple we chatted with for about 30 min). Nice breakfast consisting of cereal/juice and meat/cheese (tho I don't think the last time he had the meats - cold cuts - maybe people didn't want it) and toast/rolls/lovely peach jam filled croissants, coffee/tea.
I tried booking them last year when we went, but my mom was with us. They do have an apartment as well, but it was booked up and we wanted to have a private bedroom, so I went with an airbnb instead which was fairly nearby to that. It ran about $150 a night. But as a solo traveler, you could probably find cheaper airbnb's. I do like getting to chat with people at B&B's (we seem to end up talking with other guests whether we are in Italy or California). Hotel's are def more impersonal. But I guess it's whether you are a people person or not...you can get airbnb's that are a room in someone's home, so you could interact with the people who live there (we've done this as well and have met some lovely people!)