Horseshoe Meadows have two camping areas. If you get there at a reasonable time in the afternoon there are usually available spots. I have only seen if full once, late in the day and probably a weekend. No reservations needed and it seems like the camp sites are about $6 per night.
You can also day hike many peaks around the area without a permit. That would include Wanoga peak (off the road coming in), Trail peak, Cirque peak or the 19 mile round trip 14000 foot Mt. Langley.