http://travel.mt.gov/categories/primaryresults.asp?Title=Montana+Private+Campgroun d&Region=&SiteID=&SiteTypes=&Activities=&Services= &DiscountsCode=&ServiceCity=Sheridan
Pretty nice site; lists campgrounds (private and public), fishing accesses, USFS cabins, flyshops and other stuff. Just pick a town near where you want to go and pull up the info. May not have everything but it's pretty comprehensive. Enjoy.
Regards,
Scott
