The most interesting shop I've found in Venice is Beppe Patitucci's. Here you will find items such as $150,000 Baroque landscape paintings, important bronzes, a Doge's cap from the 1700s, old Leicas, 20th century art and photography books, but most important, Beppe Patitucci. He can entertain you for hours with stories (in English) about art, Venice, and Italy. One caveat: he isn't in his shop very often, so you might have to swing by a few times. Ten minutes walk west from San Marco: 30124 Venezia, San Marco 2511/B, Campiello de la Feltrina, tel/FAX (041) 523-6393.
If you are willing to spend $100 you can get a nice 18th or 19th-century etching of Venice at Grafica Antica, run by Manlio Penso. Penso also has valuable and rare English and Italian prints. Via XXII Marzo, 2089, 30124 Venezia, tel (041) 522-7199. Across from the Bauer Grunwald hotel, five minutes west of Piazza San Marco.
Most of the people who make and sell masks themselves are clustered around San Giovanni e Paulo in Castello. Barbaria Delle Tole is a profitable street in which to hunt. A good place to start might be Giorgio Clanetti's Laboratorio Artigniano Maschere, at 6657 (tel 522-3110). Clanetti makes a lot of paper mache masks and decoration for local theater, but also sells to the public.
Most Murano glass is
wicked ugly. If you want to see some nice stuff without leaving San Marco, go
into Pauly, at the south-west corner of the square. On the
island of Murano itself, there are dozens of glass shops. One
of the best is Seguso, Ponte Vivarini 138, tel (041) 523 69 16. Ask for Mario
Rossi and tell him I sent you. He took me out back to a workshop where I got to
watch Maestro Barbero turn a big hunk of glass into a $1200 glass
horse.
If you ignored my photography advice and end up needing to buy film or, God forbid, a camera in Venice, then try Foto Aguiari at Strada Nova 4302 in Cannaregio (tel 522-4031), just across the Grand Canal from the Rialto Markets (if you take the gondola traghetto, you'll be practically on top of the store). Here you can buy Fuji consumer and professional film, a Canon EOS-5 body, or even a Rolleiflex. If they don't have what you need, ask for directions to another shop nearby.
A lot of shops are closed on Monday morning.