To me, shopping in Venice means Murano glass and fine paper products, the occasional fashion item.
Some favorite shops:
Essegi Art Murano (Cannaregio, 6060). The shop represents five Venetian artists; the jewelry is one-of-a-kind and not too expensive.
Rialto 79 (Perle Veneziane, 79). A real find amidst all the cheesy tourist stalls and shops. Simple and chic earrings, bracelets, and necklaces made in Murano (the city is awash in Chinese imitations) and priced fairly. (See photo)
Nicola Tenderini (Ramo Toletto, 1183B). I always pick up a watercolor postcard or three here to remind me of Venice when I am home. There are also notebooks, cards, and other paper products.
Malefatte (Santa Croce, 495B). This boutique (its name means misdeeds in Italian) sells goods made by the inmates in the city’s jails. Beauty products, leather-bound notepads, and (very cool) silkscreened t-shirts and canvas bags.