The San Francisco Railway Museum packs a lot into its one room. The history of the city's transit is full of corruption and activism, and it's all spelled out in the museum displays. There are cases full of great old tickets and passes and postcards, and you can watch a film taken from the front of a cable car just days before the 1906 earthquake. And be warned: if you have a child, it may be difficult to pull them away from the replica car that they can pretend to drive. The souvenirs--witty t-shirts, retro posters--are cool too. It's just steps from the Ferry Building, and it doesn't take long. Fun fact: Maya Angelou was once an SF streetcar conductor.