Unfortunately, I haven't afforded myself many opportunities to camp in Glacier's backcountry. Working at the Many Glacier Hotel, I've often opted to undertake a few long day hikes and climbs on my days off instead. Thought I would chip in my two cents on the few sites I've stayed at in the park.
Upper Kintla Lake and Hole-in-the-Wall have already been referenced, and they are both fantastic. Hole-in-the-Wall without a doubt has to be one of the finest backcountry sites in the park.
Red Eagle Lake (head) - Nice campground, situated on the edge of the thick forest south of the lake. Probably better views from the campground at Red Eagle's foot (Split Mountain is particularly stunning from this vantage point), but nonetheless, a nice, quaint site. Great beach to hang out at very near the sites and the food prep area. Watched a family of moose at various points in the lake during our two days here. We intended to use this site as base camp for a climb of Red Eagle-Mahtotopa-Little Chief, but our large group got a late start on summit day and we opted to bushwhack the circumference of the lake and spent the day fishing, lounging, and drinking wine.
Ole Lake - Ole Lake is secluded, surprisingly beautiful, and offers fun fishing for small brook trout. We hiked over Firebrand Pass on day 1, leaving us 16 miles along the Ole Creek Trail to the Walton Ranger Station on day 2. Scary ford of Ole Creek in mid July 2008; this trail doesn't see much activity, so the only bridge is found at its southern terminus at the Walton Ranger Sation. Over the entire 24 mile duration of our trip, the only other people we encountered were trail crew. The hike from Ole Lake to Walton is long, and doesn't afford much in the way of scenery, but the forest was lovely, the vegetation thick and interesting, and the few open areas we stopped to rest were truly beautiful.
From the north shore of Ole Lake (campground is near the southwest corner of the lake), Summit Mountain (L) and Little Dog Mountain (R) loom in the distance.