This is a much longer hike than Lake Lagunitas -- about 3.5 miles around the lake. There are two very different sides to this lake -- the shady side and the very sunny side. The trails are for hikers only, no bikes allowed on almost all the hike route. There are a number of fishing spots around the lake, so you will see folks fishing along the way.
This hike starts from the Lagunitas Picnic Area part of the parking lot. The shadyside trail is a single track well worn trail just across the bridge from the picnic area.
After passing a restroom and observation deck, there is a good shortcut at the telephone pole along the road. This shortcut trail connects with the Pine Point trail. Keep to the right to keep on the trail closest to the lake.
We saw a couple lizards and a snake along the hike.
There is one last intersection, but again, just keep to the right closest to the lake for the way back to the parking lot.
Another option is to start on the Sunny side of the lake and do this hike in reverse -- so you end the hike on the shadeside trail. Its probably a better option on hot days, so you end the hike in the shade. If you do that option, just look for the start of the hike by this pipe structure.
This is another great hike in the Marin Municipal Water District and a bit more enjoyable than Lake Lagunitas. The trails are pretty much unmarked, but its hard to get lost as you just stay to the right and choose the trails closest to the water. In any case, the MMWD has a nice PDF map available of the area.
View Bon Tempe Lake in a larger map
Basics:
Area - Marin Municipal Water District's Mt. Tamalpais Watershed
Trails - Shadyside trail => Bon Tempe Dam => Sunnyside Trail => Sky Oaks Road => Pine Point
Map - Visitor Map
Length - 3.5 miles Loop hike (Easy hike, but can get hot on sunny side)
Trail - Well maintained dirt road and trail
Dogs - Yes, on a leash
Bikes - No (except on road and dam)
Views - Views of the Lake and Mt Tam along the way
Getting There - See the end of this post
Fee - $7 per car at Park Entrance Pay Station ($20s not accepted)
Weather - Some sunny spots, otherwise mostly in the shade
Other Trails - Yes, connects to Berry trail, Rocky Ridge Trail,
Facilities - restrooms and water at the trailhead/parking lot.