For science stuff in the bay area the best resource is probably http://www.bayareascience.org/ Follow the twitter feed and you'll see there are generally 4 or 5 things a day going on just in science related fields.
For art/social things I generally check out squidlist.com, but many other sites like sfist.com have a ton of things to do listings daily.
Plus there's just a ton of orgs in and around the city that have ongoing lecture series type of events. Asian Art Museum, Cal Academy of Science, Grey Area Foundation For the Arts, Friday's at the DeYoung, etc.
Tons of stuff...and a lot of it goes on outside of SF proper too with Berkeley and Stanford being so close.
I concede that there are museums. I question whether they're in the same league as their DC equivalents.
DC's museums are world class. SF can't compare very well in most instances (The asian art museum is really nice...the shanghai exhibit was great...but now gone). Also, DC museums are free which is really nice.
In the OP I wasn't really talking about the museums themselves though. More about lectures, book clubs, science/art/literature cafe's, etc.
I grew up in Alexandria and lived in Reston for 6 years. Yes, reston is far out...but that's where work was. 5 minute drive to work in the DC area? Sign me up!
Enough to spoil a person. Thank you taxpayers!