Keeping my 2 years old son busy

Can anyone give me advice on how to keep my 2 years old son and I busy?  I play with him in the morning and around 11:00am I take him for a walk so that he can take a nap from 12:00pm - 1:30pm.  In the afternoon is where it is challenging.  After he wakes up I feed him we both end up watching TV all day.  I'm looking for activities in the afternoon here in the EastBay Concord/Pittsburg area where my son can play with other kids.  Any groupies in Concocord/Pittsburg area let me know.