Hike: Redwood Regional Park
This hike is pretty civilized, what with one part having park benches and the paved trail with a dashed yellow line down the middle (there's even a speed limit!).
Despite the civilized location, the Sawyer Camp trail is quite lovely. It brings you right up to the gorgeous Crystal Springs and San Andreas lakes -- you know, the ones you see along I-280. Even for the Bay Area, this area is exceptionally beautiful.