One could backpack into Loon Lake, too. There are some great campsites near the lake, but a lot of people go there, so it's not, shall we say, "secluded." Car camping at Chinook Campground, the Loon Lake trailhead, also is a beautiful spot.
Check out this video on YouTube about mountain biking the Loon Lake trail by Kevin Mullin of Boise. It's got great flow ... just like the ride itself.
Loon Lake is a major-big mountain lake. It's more than a mile across. You might see a moose or a loon. Certainly a merganser. But one thing that's really neat about Loon Lake is that the water is shallow, so it warms up nicely by this time of year, and you can swim a long ways out into the lake and really enjoy it. (I have a story about Wendy swimming naked out there -- and getting stuck out there -- when some Boy Scouts showed up, and she couldn't come back into shore for some time!) Most high mountain lakes are so fricking cold that you can't do anything more than a quick skinny dip! Wendy was out there for like 20 minutes!
There's also a plane-crash site on the west side of Loon Lake that provides information about these guys who miraculously landed a B-23 Dragon bomber in the snow in the dead of winter and survived. They hiked out, and they were 50 miles from civilization! Whoa. It's worth hiking to the wreckage site if you haven't done so already. The Forest Service has put up interpretive signs that tell the story.
Check out the wildflowers along the way to the lake. Watch for salmon in the Secesh. And hit Burgdorg Hot Springs after your trip, if you're so inclined.