The Tuolumne is rafting Nirvana. The Forks of the Kern is even better in almost every way except for the two mile hike to put-in. There actually may be too many rapids for the normal person, but if nonstop whitewater is your cup of tea then you need to do this run.
It's called "the Forks" because you put-in just below the confluence with the North Fork of the Kern and the Little Kern. You'll run about 40 Class IV rapids with three Class V's scattered among them. The Class V rapids are Vortex, Westwall, and Carson Falls. These rapids deserve a scout as well as many of the Class IV's, so most groups usually do the Forks in two or three days even though it is only 17 miles. The only way to describe the whitewater is "awesome."
This is a place you won't want to leave. You'll stay at some of the best river camps in California and hike up to some amazing waterfalls. Most groups stop around mile eight to view the life-affirming Peppermint Falls. Another common (mandatory) stop is around mile 14 where Dry Meadow Creek cascades over granite and falls into the river.
The Forks is also very popular for it's views of the Needles. These are 3000 foot tall granite spires that once served as a fire lookout for the Golden Trout Wilderness and surrounding areas. They are a constant reminder that you're in the Sierra Nevada Mountains. Some of the river camps have a great view of the Needles as well.
The Forks of the Kern is a difficult wilderness run and there is not much of an opportunity to hike out due to the rugged country. You'll want to be surrounded with competent people and carry the right safety equipment. Even experienced rafters should consider hiring a professional outfitter for their first trip down.