We stayed at the Hotel Cavalletto e Doge Orseolo which is, at most, 2 minutes from St. Marks plaza (over a foot-bridge by, and overlooking, the gondola basin at the rear of the plaza). Its a 13th century structure with modern amenities. Price was reasonable (for Venice), location fantastic, and since it is part of Best Western, you can easily reserve it on-line.

Perhaps you know this, but for the benefit of others, Best Western in Europe is a means by which independent and in many cases really charming hotels can connect with a world-wide resevration system. Absolutely not to be confused with cheap hotels along the Interstate!