I tried one this past weekend called Hilltop. It's small, but nice, with some terrific views of Morrison, Minarets, and R & B. Turn on the road 6 or 7 miles south of Mammoth off of 395 where the green church is, travel 3.4 miles until you reach a dirt road on the left, take the dirt road 1/4 mile and park. Follow 200 ft path across a marsh via some wooden pallets.
There is a book on Sierra hot springs that describes this and others. I can't remember the title right now, something like "Hot Springs of the Eastern Sierra."
Michele went to a different hot spring and had a Baby Ruth/Caddyshack experience (except with the real thing). :-P
There are several hot springs in the Long Valley, most of them have good views of Morrison. There are several Hot Springs guide books that cover the area, they are available at Wilson's.
Just south of 203, you come to the Hot Creek Hatchery Road leading east. It's pretty well marked.
The Hot Creek geological site has huge pools of mixed hot/cold water and is extremely popular . If you want a little more seclusion, continue E along Hot Creek Hatchery Road, past the Hot Creek geological site itself, until you get to the intersection. The intersecting road is the Whtimore road, which intersects the Benton Crossing road a couple of miles S. The dirt roads leading E from the Whitmore road mostly end up at pools. These are pretty small and secluded and clothing optional.
The Hot Tub is the most popular of the small pools, there are almost always several vehicles there. On my last 3 attempts, the locals had drained the pool for cleaning. It takes about 4 hours to refill. I think they keep it clean by keeping it drained whenever the tourists want to use it!
The other small pools are a little lower key and don't get drained as often.
Nothing like a good soak in hot spring with a cold, refreshing beverage after several days of camping and hiking!
According to Secor the NW couloir has been climbed and has been called the Y Couloir and the "Death Couloir," presumably due to loose rock. He says that it is only safe when it is completely full of snow/ice from the bottom to the top. 200' of WI3-4 followed by moderate (30 to 40 degree) slopes. It is also included in Moynier and Fiddler's Sierra Classics
The section that appears discontinuous in this picture is actually continuous, but looks very sketchy from below.