If you like Free Range camping, there tends to be a lot on the road to Granite Hot Springs, which is also where you put in for the Hoback. If you need pit toilets and tables, there is a Campground a couple miles from the hot springs, and about 7 miles from the put-in. The hot springs are definitely worth checking out!
There are also campgrounds along the Snake River between Hoback Junction and Alpine, but depending on the time of year, campsites are harder to come by, and are typically more jam packed then the Granite campground is (probably due to the 10 mile each way drive). Like I said though, if you can free range, there are some good sites up along Little Granite Creek, which is very close to the highway and put in (not so close you can see or hear the highway).