Update:
Lake Aldwell is now gone, with the removal of its dam, but other features remain as described here. The former lake-bed is growing back in a jungle of saplings & brush. One visitor in 10,000 might stop for the easy-quick check.
Lake Aldwell is the impoundment of the Elwha River above the lower of the two dams on it (both slated for removal in 2011).
The main local two-lane road through this region, Highway 101, makes a moderately steep descent from the east, to the bridge crossing the Elwha a short ways above the upper end of the lake. This slope forms the eastern side of the lake, and at the top just before the road descends, is a large paved pullout & viewpoint. There are views down to Lake Aldwell, and excellent views further upstream of the Elwha River valley and surrounding terrain, within Olympic National Park.
The hillside along the western shore of the lake are public DNR State timberlands (locally refered to as Kelly Mtn). A gravel logging road runs along the lower, eastern slope of this hillside, from Eden Valley Road (mileage from Hwy 112) to Highway 101 in Indian Valley. It is not close to the lakeside, but a hike through the woods of a quarter to a half an hour brings one to the shore. The upper (southern) part of the lake is much easier to get to this way.
There is a public boat-launch on the western shore, at the upper end of the lake.