Hey Paul!

My friend just sent a great link to the biking/running routes in the Presidio, which is pretty cool if you live in the northern part:
http://www.presidio.gov/NR/rdonlyres/9DE6832B-2937...

Then there is a pretty good website by the SF Bike coalition here: http://www.sfbike.org/?maps that has tons of maps for both road and trail

I want to do this bike around SF too at some point! http://www.sfgate.com/cgi-bin/article.cgi?f=/chron...

If you want to leave SF to bike, there's the Bay Trail from Albany to the Craneway in Richmond. Fabulous and level.

If you're looking for a commute to downtown from Golden Gate Park or vice versa, many bicyclists have recommended "The Wiggle." I haven't personally tried it, but this route is specifically routed to avoid the hills of SF. Here is a link to the details of the route:
http://www.bikely.com/maps/bike-path/San-Francisco...

Also the SF Bicycle Coalition has a great map, check it out here,
http://www.sfbike.org/?maps

Cheers!