I was just looking at a Hunt-X topo map of this canyon and I see that there are a couple trails to the bottom. I don't think they're for the faint of heart, though. They cross a whole lot of topo lines. I took the photos from the end of the blue line in the top right where there's a view point. There's a fence there now but in the past, you could hang your toes over the edge and look straight down. It would give you the willies knowing your first bounce wouldn't be for 100' down.
From what I've read the road to the put-in for floating the Bruneau is pretty steep and dicey, too. Considered a Class V road:
"Put in: The traditional put in for the Bruneau is at Indian Hot Springs, just below the confluence of the Jarbidge and West Fork Bruneau Rivers. Driving there requires a capable 4x4 vehicle with good, mud-terrain tires and an experienced off-road driver. Two spares tires and high lift jack are highly recommended for travelling the Bruneau backcountry. The drive should not be attempted during wet or snowy weather, which is frequent during boating season. To get there, turn off approximataley 30 miles out the Clover Three Creek road (measured from the take out). Watch for a sign on the right after crossing Clover Creek and making a large switchback turn. The first six miles of the road are good, but don't be fooled, it quickly deteriorates into ten miles of treachery thereafter. As a general rule, stay left at the unmarked forks, and mark your turns to avoid getting lost on the way out. There are no landmarks in the flat Sagebrush plain. In the last 1.2 miles, the road drops 1,000 vertical feet to the canyon floor. There are several steep sections with exposed bedrock ledges that require high clearance. Near the bottom is a slippery clay bank that requires sidehilling, and is nearly impassible when wet. Do not underestimate the difficulty of this road. Shuttles can some times be arranged in the town of Bruneau. Due to the diffficult access, many paddlers start on the nearby Jarbidge River "