The nicest campgrounds in the area are in the Newberry Volcano [1] area. The creek-side McKay Crossing (541/383-4000, www.fs.fed.us/r6/centraloregon [2], $6, no drinking water) is about 3 miles east of U.S. 97 on the road up to Newberry Volcano.
Paulina Lake [1], Little Crater, and East Lake [1] (all $16, drinking water) are the best bets up at the top of the Newberry Volcano.
La Pine State Park (541/536-2071 or 800/452-5687, www.oregonstateparks.org [3], year-round, $22 tents or RVs, $42 rustic cabin, $81 deluxe cabin) is a large campground south of Sunriver [4]. Look for a sign on the west side of the highway marking the 3-mile-long entrance road located 8 miles north of La Pine off U.S. 97. The campground offers such amenities as flush toilets, firewood, showers, and a laundry.
This area also has one of the tallest ponderosa pines in Oregon (191 feet), close proximity to the Cascade Lakes Highway [5], and an array of volcanic phenomena.
Links:
[1] http://www.moon.com/destinations/oregon/central-oregon/sunriver/sights/newberry-national-volcanic-monument
[2] http://www.fs.fed.us/r6/centraloregon
[3] http://www.oregonstateparks.org
[4] http://www.moon.com/destinations/oregon/central-oregon/sunriver
[5] http://www.moon.com/destinations/oregon/central-oregon/cascade-lakes-highway