So, you'd like some internet. Unfortunately, you are in the USA so your options are limited. Fortunately, San Francisco has some pretty good options by American standards.
The Big Boys
Known for their terrible customer service, bandwidth caps, and general spinlessness, big ISPs offer reasonable speeds for reasonable prices. Sorta.
- AT&T -- Offers DSL and U-Verse
- Comcast -- Cable
- Astound -- Cable. I think over lines owned by Comcast. Not available everywhere in SF.
The Little Guys
- Sonic.net -- Based in Santa Rosa (about 50mi north), sells ADSL 2 over AT&T wires. Has "fusion" service in most areas that's 20Mbps / 1Mbps up. Better customer service than any of the big boys, and has a perfect score for respecting your privacy from the Electronic Frontier Foundation (an amazing digital rights advocacy nonprofit based right here).
- MonkeyBrains -- Based in San Francisco, sells wireless point-to-point access in certain neighborhoods.
The other guys
- Webpass provides insanely fast Internet (100-200Mbps) to residential units, but they require a building that's 1) built after 1995 2) has 20 or more units. So, in other words, you've got to live in an expensive condo to get it. Damnit.
Evaluating ISP performance
A great dataset for looking at ISP performance is this speedtest.net page.