Valley View
Valley View (sometimes called Gates of the Valley) was one of Ansel Adams' favorite spots. I like it not only for the classic Yosemite views, but also for the variety of compositions it offers. Unlike Tunnel View, there are a wealth of foreground opportunities here that vary from season to season.
Most photographers hop out of the car and start with the "classic" horizontal compositions that include El Capitan, Bridalveil Fall, and Cathedral Rocks with the Merced River in the foreground. Once you get these essential basics out of your system, try some vertical compositions of El Capitan. Just downstream from the parking lot, you'll find the river, with its rocks, rapids, grasses, and reflections, makes a nice foreground for these vertical compositions. A little upstream are nice views of Bridalveil framed by trees.
If you're fortunate enough to be in Yosemite during a snowstorm, head to Valley View to catch snow-capped river rocks with El Capitan emerging from swirling clouds in the background. Mid-spring is the best time catch the nearby dogwood in bloom. Valley View's best reflections are in autumn, when the water is low and reflection can be decorated with a colorful assortment of leaves. The best time of day for reflections are when El Capitan is fully lit, but the river is in shadow, either early morning or late afternoon.
Winter sunsets are when El Capitan gets the nice warm, late light photographers covet; in summer Cathedral Rocks and Bridalveil Fall receive the late light. Valley View can also be nice at sunrise if there are clouds to catch color in the east. It's often worth hanging around 20 or 30 minutes after "official" sunrise to photograph the first light on El Capitan.
How to get there
To find Valley View, drive west on Northside Drive (the only way to exit Yosemite Valley); about 3/4 of a mile beyond the Bridalveil Fall view (not to be confused with the Bridalveil Creek viewpoint described earlier), look on your left for a paved parking area with a dozen or so diagonal parking spaces; pull into an open space and the view is right in front of you (no hiking required).