So, it isn't hard to find places where you can pay to use the trails, but can anyone tell me where some good spots are to tour for free? It has to be something pretty easy, since my wife is a beginner.
I assume you are referring to typical no wax XC skiing? If so, try Grass Lake at the top of Luther Pass (Hwy 89). Another good tour is to park at Schneider Cow Camp (Hwy 88 at Caples Lake Caltrans Station) and ski into Meiss Meadows. Both are fairly flat and a good ski.
In South Lake Tahoe, park at the top of High Meadows road off Pioneer Trail and ski up to high meadows. And of course, if you want the easiest ski, park at Camp Richardson on (Hwy 89 N) and simply ski the shoreline of Lake Tahoe between Eagle Point and Pope Marsh.