The East Fork of the Carson flows with the melting snow, and heads east down the Sierra Mtns, into Nevada.  It’s a class II+ run, but moves quickly.  We did a trip a few weeks, with the great folks from Current Adventures (http://currentadventures.com) who do lessons and trips all over northern california.  (full disclosure, I work for CA some).  We tagged along on the trip.  The rapids were fun, the scenery was great, the food was yummy, and the company was wonderful.  Highly recommend trip.