Fire Lookouts are a great way to experience the mountain world. I just discovered a Boise National Forest brochure (linked below) that covers most of the existing fire lookouts on the forest and provides brief access information for each. (All of these mountains have pages on this website.) Fire lookout sites were chosen because of their commanding views. You will find on a visit to any of these lookouts that the Forest Service choose well. The views are uniformly impressive.
Boise National Forest brochure link: Sentries at the Skyline
I would note that I believe the Forest Service has underestimated the difficulties of most of the access roads. I recommend a 4WD or at least a high clearance vehicle with good all terrain tires if you are going to visit any of these lookouts.
In addition to the manned lookouts the brochure also lists five unmanned lookouts: Bear Valley Mountain, Thorn Creek Butte, Meadow Creek, Rice Peak and Swanholm Peak. (Photos and links are found below.) The lookout structures are still present on these mountains but they are no longer used. Many other mountains in the Boise National Forest were used as fire lookouts in the past. You can research these and many others at firelookouts.com or Idaho Lookouts.
The brochure also mentions the Deadwood Lookout but gives no directions. Deadwood Lookout is available to rent through recreation.gov. Be forewarned this rental is extremely popular. You will need to reserve many months in advance.
Finally, the brochure does not include Shafer Butte (at the center of the Bogus Basin Ski Resort), Hawley Mountain (near Horseshoe Bend) and Pilot Peak (near Idaho City). These lookouts offer great views and are also worth visiting.