I visited Ardenwood Historical Farm a while back when our youth group made a field trip there. This farm is home of the Patterson Ranch, a luxurious Victorian mansion and botanical garden. The farm is still operational, and grows organic crops throughout the year, which are sold near the main gate area. It's a welcome change of pace for city folk, as you get to experience (and even take part in) 19th century farming and agricultural practices. Admission is cheap, around $5 when I went there (probably about the same today).