Hi!  I had a lot of success with Raisingthem.com with a small playgroup I started in Baltimore, MD.  There were only eight of us, but we quickly became wonderful friends and met regularly through this site.  I'm hoping to meet a few nice moms/kids again here in San Francisco.  My children are age 3, 1 and another on the way, so new moms are welcome as well as those with older toddlers like my son.  Please let me know what sort of playdates you are interested in.