Saddle Mountain Overlook, Grand Canyon NP
Probably offering the most spectacular views of the North Rim, Saddle Mountain Overlook has only a few previously-used places to camp, although dispersed camping is technically allowed anywhere as long you don't drive beyond 30 feet from the side of a road.
Forest Road 310, Grand Canyon NP
Also known as "Coconino Rim Road", the first mile of this road starting from Highway 64 is off limits to camping due to being within a one mile radius from Hull Cabin (see rule in Downloads below). You generally have to get south of the intersection with Forest Road 307 before getting to the dispersed camping area.
Long Jim Loop, Grand Canyon NP
Long Jim Loop is a 3/4 mile dirt road encircling the northwest portion of Tusayan Village. It's a forest road open to dispersed camping. There are about a couple dozen previously-used sites here. The forest's policy of remaining within 30 feet from the side of the road still applies here.
Forest Road 302, Grand Canyon NP
Forest Road 302 starts at Highway 64 inside the town of Tusayan and heads east. Historically, the first 1/4 mile of this road was off-limits to camping, but it seems these days there are often people still camping within this restriction. Still, even when you get past the 1/4 point, there are dozens of previously-used sites to choose from.
Forest Road 688, Grand Canyon NP
Forest Road 688 heads east from Highway 64. The first mile of this road is off-limits to camping because it is within one mile of a developed campground (10X Campground). But when you get past that range, there are dozens of previously-used campsite, as well as dozens more along spur roads branching from it.
Forest Road 305, Grand Canyon NP
The first mile of Forest Road 305 has dozens of previously-used dispersed campsites, as well as dozens more along spur roads leading off from it. The road itself is firm packed dirt suitable for any vehicle or RV, but don't stray too far off road as the dirt gets soft.
Hackberry Lake Campground North
This is a developed campground intended for OHV riders, but is also used by RVers visiting Carlsbad Caverns and the town of Carlsbad. There are 12 campsites here, each with a covered picnic table. Some of the sites have cooking grills, and a few have a trash can. There is also a vault toilet here.
Hackberry Lake Campground South
This is a developed campground offered by the Bureau of Land Management for free. The BLM officially designates this for "Overnight Use", but most people here stay here over a weekend. There are about 8 to 9 campsites here with picnic tables, fire rings, and a vault toilet.
Chosa Campground, Carlsbad, NM
This is a large open space created by the Bureau of Land Management specifically for RV camping. It's located about 30 minutes south of Carlsbad, NM, and about 20 minutes south of Carlsbad Caverns National Park Visitors Center. The only amenity is a trash dumpster.
Aden Hills OHV Area
This is a large, desert flat set aside by the Bureau of Land Management specifically for OHV use. Most of the camping is set up at a staging area close to the County Road. There is an old shade structure there with an information kiosk. You can also camp in other areas, but you'll be subject to OHV riders speeding by your camp.