Prospect Peak Trail is a 6.9 mile out and back trail located near Westwood, CA and is rated as moderate. The trail is primarily used for hiking and is accessible from July until October.
This was actually probably my favorite trail in the Butte Lake area. The climb is a bit tough - just a long, fairly steep climb that gradually gets steeper, but once you're on top the views are probably the best on that side of the park. It is a volcano, but it has only a shallow, sandy crater covered in trees, so it's hard to tell. The trailhead is right outside camp on the way to Cinder Cone, so this should be a mandatory hike for anyone staying at Butte.