Union Pacific's (used-to-be:  Western Pacific) Feather River Canyon is an interesting strech of railroad to observe and a scanner really brings the railroad action to life.  I've listed the frequencies that you should program into your scanner to follow the action.

160.515 - Omaha Dispatcher 10, Stockton, CA  to Winemucca, NV.

160.470 - Omaha Dispatcher 10, Reno, NV area.

160.290 - PBX,  Sutter Butte, used in the Oroville area and the Reno area.

160.605 - PBX, Red Hill, used in the Feather River Canyon, east of Oroville.

This is not the busiest mainline in the country, as I have sat by the tracks for hours waiting for a train.  Pack a nice lunch, bring a good book to read, and keep you scanner tuned to the Feather River Canyon frequencies.