If you're flexible with your travel to Yosemite, there are some side trips in the vicinity that'd be worth considering.
Devils Postpile National Monument: Long ago a part of Yosemite, the Postpile is a geologic and biological wonder in the Eastern Sierra. Located just about 35 miles (56 km) south of Yosemite’s Tioga Pass Entrance, the western half of the 800-acre monument reveals the granitic underpinnings of the High Sierra, while the eastern half reflects the volcanics of the eastern Sierra. Indeed, the "postpile" was volcanic in creation.
Devils Postpile National Monument takes its name from this contorted outcrop. Kurt Repanshek photo.
The monument also is relatively biologically rich, located as it is at the convergence of 3-4 bioregions (eastern, western, southern Sierra, and possibly the northern Sierra). Not only is the valley that the monument sits in a migratory corridor for deer, but it also sees a fair amount of migratory birds and is a mixing point for eastern and western Sierra vegetation such as Red fir, sagebrush, and Great Basin juniper.
June Lake Loop: A scenic pocket between Yosemite and Devils Postpile, the this community is given over to outdoor recreation. Bordered to the west by the Ansel Adams Wilderness Area, June Lake is a good basecamp for excursions into the national forest, and even the national park beyond, if backpacking is your preferred method of travel. There also are some excellent dayhikes here, as well, and lakes for fishing.
Mono Lake: Once nearly drained dry by thirsty Californians, this lake that covers 70 square miles (113 sq km) just east of Yosemite is a destination for millions of migratory and nesting birds, and a great spot to dip your paddle. There are also interesting geological features known as tufa formations along the lake.
Panum Crater: A little under 10 miles (16 km) from Lee Vining, CA, Panum Crater is part of the Mono-Inyo Craters chain just south of Mono Lake and east of the Sierra Nevada Mountains. A dome surrounded by a tephra ring, the trails at the crater bring you up close to pumice and banded obsidian in addition to panoramic views of Mono Lake and the surrounding landscape.
