Five that are worth the effort:
Santiago Peak via Holy Jim Trail: 16.1 miles roundtrip with 4,000 feet elevation gain. Follow Holy Jim Canyon Road half a mile to the trailhead, and then four and a half miles to Main Divide Truck Trail (3S04). Go left; another three miles, and you'll reach the summit. Park at the intersection of Trabuco Creek and Holy Jim Canyon roads in Trabuco Canyon (4.7 miles from the intersection with Live Oak Canyon). Trabuco Creek Road is a rough dirt road.
West Horsethief and Trabuco Trail Loop: 10.5-mile loop with 2,500 feet elevation gain. The single-track trail begins at the end of Trabuco Creek Road. Go left at 1.7 miles on West Horsethief Trail, right at 4.5 miles on Main Divide Truck Trail and right at 5.8 miles on Trabuco Trail, which leads back to the trailhead. Parking area is one mile past the intersection of Trabuco Creek and Holy Jim Canyon roads (see above).
Caspers Wilderness Park. Enjoy the park's 8,000 acres and more than 30 miles of trails. 33401 Ortega Hwy., San Juan Capistrano.
El Moro Canyon. There are many trails to be explored, including a 6.8-mile loop. Pacific Coast Highway and El Moro Road, Laguna Beach.
Whiting Ranch Loop: Six miles with 600 feet elevation gain. Off Portola Parkway, a few hundred feet past Ralph's supermarket, Foothill Ranch.