There are 19 churches in the sestiere of San Marco (which includes the island of San Giorgio Maggiore).
My favorites in this sestiere are the Basilica, of course; San Salvador (a beautiful church with an amazing Titian Annunciation); and San Giorgio Maggiore (awesome views from the campanile and a gorgeous church with some great art).
I also like Santo Stefano with its leaning tower and wooden ceiling.
San Vidal has a painting by Carpaccio on the high altar (see left); the saint is riding a horse that was supposedly modeled on one of the four horses of San Marco.
Chorus Pass churches in this sestiere are Santa Maria del Giglio and Santo Stefano.
Churches in San Marco
Basilica di San Marco
San Bartolomeo (San Bortolomio)
San Beneto (San Benedetto)
San Fantin (Madonna di San Fantino)
San Giorgio Maggiore
San Vidal (San Vitale)
San Zulian (San Guiliano)
Santa Croce degli Armeni
Santa Maria del Giglio (Santa Maria Zobenigo)
Santi Rocco e Margherita (Ss.Rocco,Stefano e Margherita)
At the top of my “wish list” for this sestiere is San Fantin which is very close to the newly reopened La Fenice. I’ve been by this church many times but it’s never been open. It supposedly has (or had) a miraculous image of the Virgin that was brought to Venice from somewhere in the East.
Currently, there are three campanili (bell towers) that you can go in (and up) in Venice, and two of them are in this sestiere (San Marco and San Giorgio Maggiore); the third one is on the island of Torcello. There are plans to open the campanile of the church of San Salvador soon, which will give us another view from above with a different perspective since San Salvador is closer to the Rialto Bridge. I’m psyched about this! I hope it's open in December.
Update, Dec. 2007: Learned that San Fantin is closed indefinitely for restoration. I also learned that San Teodoro is a church not an oratory so I've moved it into the church list.
A lady at San Salvador told me that their campanile project is stalled. Oh well, stay tuned.