San Francisco Electric Tour Company - two hour tour on Segways --2 wheel electric scooters

Go Car Rentals - it's a little pricey but you'll definitely be telling the folks back home about the little, 2 seat, 3 wheel cars open air (convertible) cars that have GPS and will talk to you, telling you where you are and where to turn

The San Francisco Cable Car Website - no matter how touristy you think this is, you have to do this if you are in San Francisco. Routes, fares, etiquette, interactive ride, more

Golden Gate Transit - Ferry Service - even if you are not coming from Marin county to the north, it'll be worth the fare to ride the ferry in SF bay and see great views of the city, both the Bay Bridge and the Golden Gate Bridge, Angel Island, Alcatraz islands, and even San Quentin prison (on the Larkspur route)

BART - Bay Area Rapid Transit - subways, trains connect San Francisco to the South and East Bay

Muni - the bus system, not for the faint hearted, but worth a ride to watch the fearless bus drivers negotiate the streets

Taxi - It's a small city, so don't sweat a cab ride. List of cab companies with phone numbers, Luxor, Veterans and Yellow Cab are popular ones

Golden Gate Transit - Bus Schedule - buses are more luxurious than Muni buses, service from Marin and Sonoma counties to San Francisco

Blazing Saddles - rent a bike in San Francisco for in the city, or better yet, ride across the Golden Gate Bridge into Marin County

San Francisco Walking Tours - the hills can be a challenge but the city is small and you'll see so much more than with other methods of travel. Site has pdf maps of several popular tours