Lake Tahoe is a hiker's paradise. Here is a list of short walks in the basin, above the basin and just due south of the basin. All the directions can be found in two books that I highly recommend: The Tahoe Rim Trail and Alpine Sierra Trailblazer.
1. Trails in Bliss State Park.
2. Trails in Desolation Wilderness. Jumping off place: Echo Lake which is a great picnic spot if you don't want to hike and just enjoy a visit to a pristine High Sierra lake.
3. Sand Harbor. The bluest of blue waters with a long sandy beach and granite rocks to swim to.
4. Pope Beach. Nice beach and historic Old Tahoe buildings to visit.
5. Hope Valley. About twenty minutes away. A pristine valley with numerous river and meadow walks. July and August are good months to hit it when Lake Tahoe is mobbed with tourists.
6. Echo Pass, Ebbetts Pass, Monitor Pass. Drive-to's but many dayhike possibilities.
7. Fallen Leaf Lake. Drive in along a road dotted with rustic vacation cottages. Dayhike to Mt. Tallac (all dayer) or walk around the quaint village and Stanford Camp.
8. Eagle Falls Trail. Instant gratification right off the Emerald Bay Road.
9. Vikingsholm. Short hike down to Emerald Bay. Take a tour of the castle along the shore. Bring a picnic lunch.