Last time I checked you could camp at Agency Creek for free. Keep in mind though the sites are primitive so bring all the items listed in the Vanabode book. The forest is beautiful. The terrain is varied and there are outhouse style toilets here.
Directions: Leave Tendoy and go 4 miles east on the the Lewis and Clark Backcountry Byway.
Vanabode Special Notes: You're going to want to visit
Agency Creek in the warmer months from April to September. Otherwise,
you will be freezing your tail off all night. Aside from that, this is
a great place to Vanabode, as there are no fees and most of the land is
BLM. Ultimately, if you go in the summer, you'll have a great time
at Agency Creek Campground in Idaho.