Along the Grand Canal is a free PDF guide, which takes you all the way from the railway station to the extreme eastern end of the city. It's absolutely not a sight-seeing tour of the traditional kind, but if you've been to Venice before it might show you some back streets you've not seen before - and let you get away from the crowds.
Venice - Cannaregio visits one of the lesser known areas of the Venice - the ghettocity, the working class district of the Cannaregio. There aren't many palaces but there's a surprising number of marvellous churches, from the medieval Gothic Madonna dell'Orto to the baroque theatricality of the Gesuiti. And on the way we pass through the Ghetto, site of Jewish life in Venice for centuries and still a focus for the Jewish community.
San Marco to San Zanipolo (Santi Giovanni e Paolo in proper Italian) takes you from the great basilica and the Doge's palace, at the centre of the city's life, to the fine gothic pantheon of the Doges and finally to a tiny Renaissance jewel, Santa Maria dei Miracoli. It's a tour which visits many of the great sights of Venice and shows you the glories of the church and state from Byzantium to the Baroque.