Thousand Island Lakes, Mammoth
Just got back from an overnight to the hike-in sites at Point Mugu. There are a handful of first-come-first-serve sites that seem to get almost no use these days. The whole area is still pretty charred looking from the fires back in May 2013 + drought conditions so if you're going to do it, don't expect lush greenery or much shade.
Starting from Ray Miller Trailhead just north of the drive-in Big Sycamore campsites on PCH. Overnight passes are $10 from the iron ranger at the trail head. La Jolla Canyon Trail (shorter route) is closed due to storm damage so you'll have to take Backbone Trail which is a series of switchbacks climbing high above the beach and offering some great views. After 2.7 miles you'll veer left onto Overlook trail. To the NE you'll get great views of the Santa Monica Mountains and to the SW you'll have PCH and the Pacific.
After 2 miles you'll make another left for a quick jaunt of 0.2 miles to the camping area. The information bulletin is in disrepair, as are the sites themselves (lots of dry overgrowth) however a Boy Scout troop has put in new tables and food lockers and there are a few clear sites where you can comfortably camp for the night. I didn't see any water, but there is a dry creek bed running along the campsites. You can't complete the loop (due to La Jolla trail closure) so you'll have to climb back up and out the way you came. Thornhill Broome is just across PCH and does the trick for a quick post-camp swim.