Tamarack Flat on Tioga Rd. is just outside the valley, too. Yosemite Creek campground is a little further and down a long dirt road, but it's very pretty.
When you pick up your permit, you can also inquire about backpacker's campgrounds where you can stay the night before and the night after your backpacking trip with a valid permit.
There's also something you can do where you show up in the late afternoon somewhere in the valley and they can tell you if there are any no-shows for reserved camping reservations. Kind of a pain when you could be out somewhere else. But it's an option.
There are some forest service campgrounds right outside the park if you are arriving in the evening and just need a place to crash for the night. Where are you coming from? Dimond O is nice, but not sure if it's full in the summer.
http://www.fs.fed.us/r5/stanislaus/groveland/camping/dimond.shtmlIt's on Evergreen Road, the road you take to Hetch Hetchy.
There are these others too
http://www.fs.fed.us/r5/stanislaus/groveland/camping/index.shtml
