Ryan from GPS Sleds has created a a mapset of snowmobile trails in MN. These are installed into Mapsource where you can select them from the dropdown list and then upload them to your GPSr just like Garmin's detailed maps.
Minnesota Snowmobile Trail
And I created a mapset from Lake of the Woods (borders MN, Manitoba and Ontario) with approximately 800 miles of trails....which also installs into Mapsource.
Lake of the Woods Trails
Remember these are maps and not just uploaded track files...so you have all your Saved Track storage available to save tracks.
These mapsets were created with the software featured in this post
Here's a screen shot from a Garmin 276c of the trails (red) in the Young's Bay/Oak Island area of Lake of the Woods
And a 276c screen shot of most of the lake.