The Ca' d'Oro (House of Gold) is truly a sight to see, and I am not alone in thinking it's the most beautiful on the Grand Canal--which is packed with gorgeous buildings.
The fifteenth century palazzo, with its flowery Gothic facade and echoes of Byzantium, was built by the Contarini family in the early 1400's. Although it's technically the Palazzo Santa Sofia, it quickly became known as the Ca' d'Oro because the facade was actually gilded in its early days and sparkled brilliantly against the water in the sunshine. The facade was also once tinted in hues of ultramarine, black, white and gold by Flemish artist Jean Charlier. It must have been an amazing sight.
The palazzo passed through many hands--and suffered many indignities--until it was purchased by Giorgio Franchetti in 1894. Franchetti restored the damaged building and converted it to a gallery to showcase his extraordinary art collection. He bequeathed the palazzo and his art to the city of Venice at his death, and today it houses the Galleria Franchetti.
For a nominal admission fee, you can see his collections including Venetian sculpture, paintings, frecoes by Titian and Giorgione,
and porcelains, along with pieces from the Archaeological Museum, the Correr, and the Accademia Galleries. It's a fairly small museum with some lovely pieces, like this Annnciation by Carpaccio. Of course, Venetian painters like Vivarini and Guardi are well-represented, and there's a famous St. Sebastian by Mantegna. 
There are also gorgeous views of the Grand Canal out on the loggia, so be sure to bring your camera.
This is a great museum to visit if you only have a short time in Venice. It's much smaller and more intimate than the grand Accademia and yet you can see works that show the vivid colors and beauty of Venetian art.
It's easy to find, too. Just get off at the Ca' d'Oro vaporetto (water bus)stop on the #1 line and walk down the ramp. The museum entrance is on the left. Even though it no longer glows with gold, the Ca' d'Oro is a beauty worth seeing.
