You can kill a lot of time at the library of congress

This section:

http://memory.loc.gov/ammem/index.html

"American Memory"

Has a ton of cool stuff in it. Sheet music, maps, old movies, tons of scans....

Here are panoramic photos of san diego:

http://memory.loc.gov/cgi-bin/query

(not sure if that link will work)

Here is an example of a panoramic photo of downtown san diego from 5th and E st (taken in 1914)

To see the full size, click here:

http://memory.loc.gov/service/pnp/pan/6a02000/6a02200/6a02295r.jpg

Tons of stuff to see here...