Welcome to the Search and Reunion Message Board!
Do you have the state of birth for your birthmother? If so, you might check marriage records in that state. If she was born in California you might check marriages under the name Anderson in the county of your birth.
California Search Website:
Other great websites to check out:
http://www.adoptionchat.com
http://www.adoptionlists.com
http://www.adoption.com
http://www.adopting.org
http://www.adoptionregistry.com