I'm a fan of Restaurante alla Madonna in San Polo (http://www.ristoranteallamadonna.com/eng/locale.htm) and Trattoria alla Rivetta in San Marco: both are fairly simple places, with outstanding food. If you want something more fancy, there's Fiaschetteria Toscana, on the San Marco side of the Rialto, where I had probably the best meal I've had in Venice (http://www.fiaschetteriatoscana.it/); and Osteria La Zucca, near Campo San Giacomo Dall'Orio, which has an incredibly creative menu (http://www.lazucca.it/).

Bottom line, enjoy!