Henry Cowell State Park, in Santa Cruz California, is a great place for a hike through some old redwoods to the San Lorenzo River. All trails are open to hikers and some are open to horse riders and mountain bikers. Over 20 miles of hiking and forest. It is mountain lion territory and warning signs are posted. More information here: http://www.parks.ca.gov/?page_id=546
The Russian Gulch Waterfall is just a short hike from the beach at Russian Gulch State Park. The park is just north of the town of Mendocino off Highway One. Surrounded by giant redwood trees this waterfall usually doesn't have a huge water flow but if catch it right after a good rain it's an amazing sight.
Along Big Sur's rolling Pacific Coast you will find the Julia Pfeiffer Burns State Park. Famous for it's beach front waterfall, great hiking trails, and underwater scuba diving reserve. Featuring 3,000 foot tall headland cliffs, miles of coastal wilderness, and panoramic views of the Pacific. The park is named after the pioneer Julia Pfeiffer Burns.