I 2nd the Tallac suggestion. It's about 10 miles round trip. I prefer the Glen Alpine route just because the view of Tahoe doesn't show itself until the very end and it's pretty awesome! You can make a semi loop out of it by taking the shortcut up the ridge from the parking lot and then come down the main trail via Gilmore lake. It's a well trodden trail but not on most maps. Cuts at least a mile off the hike. I wouldn't do it in the afternoon as it would be hot. To find this trail go to the very back of the Glen Alpine parking lot where the pavement ends and there is a dirt road that proceeds around Fallen Leaf lake. Park in the paved parking lot and walk up this road about 100 yards and there is a dip in the road. Look to your left and you will see an obvious trail to your left. This will take you to a v-notch up the ridge. At the top - around 2 miles? - you cross a little creek and the trail continues to Gilmore lake. The better way is to leave the trail here, which will be a right turn, and continue up the shoulder of Tallac which you are basically already on. You'll come across the other trail coming up the front side of Tallac in a mile or so and can follow that up to the summit. In the Spring this is one of my favorite hikes because of the crazy great wildflower displays on the flanks of Tallac. It's pretty dry this year so be sure to carry water as the creeks may be dry.
