E.C.
I don't know about the SF/Peninsula area but over here in the East Bay, I've donated a lot of our outgrown baby gear/clothes/books at Bananas Inc. on the Oakland/Berkeley border (a nonprofit childcare referral/support/resource agency that serves many low income families) www.bananasinc.org . It's been a few years since I last donated so you might want to give them a call first, but I know they used to keep bins in their lobby where they'd put the donated clothes and books and toys and everything would be taken by the end of the day, I don't recall how they handled the larger things like the cribs and gates - they might've had waiting lists, I'm not sure.
You might also try contacting your local hospital to find out if any social workers are in need of baby gear for their clients - our local parents of twins club occasionally gets requests from social workers in need of baby gear and clothing for their clients.