Blue Pelican is a used/consignment store for marine supplies and equipment. They also sell new supplies and equipment, but as far as I can tell, they are the only spot in the East Bay that sells used marine equipment. They have a friendly staff and lots of things to rummage through. They also have a section with neat antique books and other sailing things.
They are located in the Grand Marina at 2021 Alaska Packer Place.
http://www.bluepelicanmarine.com
(510) 769-4858
Tuesday - Saturday 10am to 5pm