Thanks for the question! Waldo Lake is a true Oregon gem. The Willamette National Forest does an excellent job maintaining the webpages for this area (http://www.fs.usda.gov/recarea/willamette/recarea/?recid=4528). Their interactive map will give you the overview. Shadow Bay, Islet, and North Waldo are developed campgrounds with pit toilets and drinking water. There really aren’t bad places to camp around this lake, it’s all very natural, quiet, and close to the water. I’m sure you are aware that mosquitoes are quite prevalent in early summer. Late July is a great month to camp and enjoy the clarity of the water.
There are numerous trails in the Waldo Lake Wilderness, including the Pacific Crest Trail on the east side of the lake. Trails to Bobby Lake, Betty Lake and Fuji Mountain are some of the favorites in the area. A great local resource in Oakridge is the Willamette Mountain Mercantile. The local staff hikes, bikes, and camps in the area and all are very knowledgeable about trails and conditions.
I hope this helps. Let me know if you have any other questions I can answer.