You can't do any better than Glacier N P. Good camping/RV parks on both east and west sides. I prefer east side because more hikes start there, but you'll want to drive to both sides..
The KOA at Livingstone MT is very nice. If you like to dry camp, there are beautiful places in the National Forest. You can check on line with the Forest Service. We have camped south and east of White Sulfur Springs.
It really depends on what you want to do, really; Fish, Hike, Boat, tourist, etc.
Lots of places to go and do, what do you want to do while there?
2008 F350SD V10 with an 2012 Arctic Fox 29-5E When someone tells you to buy the same rig they own, listen, they might be right. When they tell you to buy a different rig then they own, really pay attention, they probably know something you don't.
If you are coming up through WY / Yellowstone, the Bear Tooth Pass is awesome. Come north into MT and hit Red Lodge - a great old town to hang out for a day. The Red Lodge KOA is pretty decent.
Heylea
Class A TBD in 2013
2009 Jeep Compas Rallye 4x4 5-sp manual
I really liked georgetown lake near Anaconda. Between there and philisburg there is a pay to play sapphire mine. they had a nice free campground. We have been there several times. If you are in missoula visit the smoke jumper base and rocky mountain elk foundation.
John & Judy
2007 Winnebago Access 31C
2008 Ford Focus
NFS Red Cliff Campground on HWY 191 between West Yellowstone and Bozeman, MT is a good place to camp. It is on the Gallatin River, with some electric sites, fishing, hiking, rock climbing. Sites can be reserved. There are some more NFS campgrounds on the river going north toward Bozeman. This is a beautiful drive if you are traveling through Yellowstone and come out in West Yellowstone, MT.
Dixie and the Goldendoodles, Nikkibear and Gus
2012 Roadtrek SS Agile