Bruneau and owyhee drainages. also near the snake, not sure if there are whitewater runs near that area though.
When the bruneau is at very high flows there's a play feature at one of the low head dams just below the takeout. kayakidaho.com has some pix I think.
WF bruneau, Jarbidge, Sheep Creek, EF bruneau are the IV-V runs in the bruneau drainage. The upper owyhee drainage will have a great year this year as well. Deep creek into the EF, the SF, little owyhee, 3 forks to rome are all goood whitewater runs. Garat Gorge is a V run that I hear very little about in the upper owyhee drainage.
You might check out boise boaters or IE whitewater on yahoo groups. Succor Creek is a V creek run that is getting a ton of attention the past few years. Check out the outdoor idaho video page on facebook for a recent video of the run.