Scott's Flat, CA

Scott's Flat Lake is about 90 minutes from Sacramento, California up highway 49.  The campground is big, expensive, and crowded on weekends.  They do have pay showers and reasonably nice restrooms though.  In July the lake water was perfect and swimming was great, the lake wasn't that crowded, boats and water skiing are allowed, personal watercraft are not.

Loon Lake, CA

Loon Lake Reservoir is in the Eldorado National Forest about two hours east of Sacramento, California.  It has a campground and boat ramp.  Loon Lake is at a higher elevation than Ice House Reservoir (which you drive past to get to Loon Lake), so it opens later in the year and is usually less crowded.  A general store is nearby at Ice House for supplies and showers.  My wife claims the boating at Loon Lake is superior to that at Ice House, but you really can't go wrong either way.

Ice House Reservoir, California

Ice House Reservoir is in the Eldorado National Forest is about 80 minutes east of Sacramento, CA.  It is a bit cold in June, but its the lowest elevation of the Sierra lakes on Hwy 50.  We saw a bald eagle flying around while we were on the lake.  It has a paved boat ramp, a few camp grounds, and a $7 day use fee.  Just a couple miles away is a general store where you can fill up on the things you forgot.