The Lauterbrunnen area is famous for mountainbiking. Rent an Interlaken bike for eg, there's a rental store at the West station and ride to the end of the valley the place calls Stechelberg. For sFR.20.- take your bike in the gondula up to Mürren. From Mürren follow the red bike trail signs to Winteregg. Its a easy trail for everybody not much up hill. From Winteregg enjoy a fast downhill to Isenfluh or back to Lauterbrunnen. This tour can also easy be started in Interlaken: it's only 45 minutes more biking and the round trip from Interlaken needs 3-5 hours. Get your great quality bike maps and all information at rental places in Interlaken.
Hike up to Wengwald by walking up the trail starting beside the townhall. Cross the river and follow the signs to Wengen until you see a sign pointing towards Wengwald. Hike up this way until you get great views of the Lauterbrunnen valley. Takes only 1.5-2 hours if going slowly.