Here are some of my favorite places to find races as well as a few famous races thrown in:

Active.com: great online website for finding all kinds of events

Dolphin South End Running Group: also a running group as you can guess from the name. Coordinate races nearly every week often as fundraisers. I'm always in awe when I see these runners around the city and the hills of Marin - a handful are in their 80s and would leave me at the starting line in most races.

Envirosports: awesome trail races around the year. The races are rather informal and the prize is a rubber chicken. At the start of each race the director gathers all runners to sing America the Beautiful. Prices vary but come in around $30 - less if you don't get a shirt.

PCTR: some of my favorite trail races. Courses are typically well marked, well stocked with water, and well cheered. The coordinators are ultra-marathon runners so, needless to say, the crowd that shows up are on the intense side.

The Schedule: similar to Active.com but a little easier to navigate.

Races of note:

Bay to Breakers: I realize this isn't a race organization, but this is an event to look forward to year after year. It's a 12k through the city - some people run it, some drink it, some wear costumes, some wear ... none, everyone has fun.

Dipsea: hands down one of my favorite races in the Bay Area. Also one of the harder ones to get in to. You need to apply the day this race opens and practically drive the application and check to the house of the race organizer - first come, first serve. Then, a lotto to get in.

Healdsburg Half: this is the first year of the race (and it's on my birthday), so I can't give a race update or overview. Should be a gorgeous run - how can it not with the setting?

Napa to Sonoma Half: a great mid-summer race that occurs in July. Also, a great excuse to wine taste after running. Beautiful race through vineyards, a great (huge) metal at the finish, and typically good weather.

Turkey Trot: similar to Bay to Breakers - aka, not an organization, but a race. A great fun race. A short race (only 5k). This was the run that inspired me to start running again.