The hike to May Lake is a bit of the essence of Yosemite -- expansive views over granite peaks, a sparkling blue lake set below 10,000' Mount Hoffmann, a subalpine forest, and, well, other people. This is not where you go for a solitary backcountry escape - but it is a delightful and beautiful place to take someone for their first backpacking trip or just an enjoyable day hike.
This route, the shortest way to May Lake, starts at the Snow Flat trailhead which is reached via a rough, narrow, but paved road off the Tioga Road. There is a vault toilet and bear boxes here, but limited parking. The trail moves upwards, slowly at first, but with a steadily greater incline until you hit a few switchbacks. Stop on the way and make sure to check out the views - they're great!
At the top of the hill - just off the trail is a ridge with an excellent view and a great place to stop for a snack - the trail levels out again and quickly reaches the May Lake Backpacking Camp. There are bear boxes, a water spigot, and a flush toilet (!) here, and campsites all along the southeastern shore. The May Lake High Sierra Camp is along the northern end of the lake. There is a good use trail following the southern shore that, if you follow it long enough and high enough, will take you to the summit of 10,850' Mount Hoffmann, near the geographic center of Yosemite and with great views in all directions.
The parking lot at the high trailhead fills quickly; on the bright side, most of these people are dayhikers, so early or late arrivals should give you plenty of parking.
This is a great place to take your kids for their first backpacking trip: it's short, there's a pretty lake (with rocks to toss in) at the end, there are regular toilets for the potty-trained crowd, and there will likely be other little kids there too.
There is running water and a bear locker at the campsite! Make sure everything is working before you go, though - you don't want a bear to eat your food.
The Mount Hoffmann trail goes along the south shore of the lake and is said to be a great hike, although it's very strenuous, much more so than the hike to May Lake.
On the way up don't forget to turn around and look behind you. The best views are to the south. (It's easy enough to blaze up the trail that you could forget. I nearly did.)There are 3 easily-reachable trailheads for May Lake. The shortest, from Snow Flat, requires a car and involves a narrow paved road off of Highway 120. You can also ride the Tuolumne Meadows Shuttle to the May Lake Trailhead (stop #11), which adds another 1.5 miles and 600' to your hike. There's a third trailhead near Porcupine Creek, reachable via the Tuolumne Meadows - Yosemite Valley Hikers' Bus, which is ~3 miles but only 700' of gain.