In addition al to Mother Mountain Loop [1], another good overnighter, though not a circular route, is Indian Bar.
This hike starts at Box Canyon [2] on Stevens Canyon Road, crosses Nickel Creek, then turns left to follow the Cowlitz Divide. At Indian Bar, the Ohanapecosh River divides a meadow; the shelter is on the west side, just above Wauhaukaupauken Falls.
Return by the same route for a total of 15 miles.
Links:
[1] http://www.moon.com/destinations/washington/south-cascades/mount-rainier-national-park/recreation/backcountry-hiki/mother-mountain
[2] http://www.moon.com/destinations/washington/south-cascades/mount-rainier-national-park/sights/stevens-canyon-ohanapecosh-area