There's a great loop hike you can do without having to drive from any of the main campsites in Yosemite Valley (Upper Pines, Lower Pines, North Pines). It goes up to Vernal Falls, where you can turn around if you want, or you can go another 3 or 4 miles to add the loop to and from Nevada Falls, too.
We did the full thing, and while it was a lot of UP, much of it was shaded, and the views were absolutely worth it!
Incidentally, these were basically the only two falls in all of Yosemite that actually had water in them! So, we chose well. (Peep the rainbow at the bottom of the waterfall in the first photo!) We did a bit of scrambling to get closer to Vernal Falls; some people were swimming in the pool forming at its base. While tempted to join them, we decided to continue the ascent.
Once atop Nevada Falls, we stopped for lunch. Relishing the break, we stripped off our shoes and socks and soaked our swollen, dusty feet in the cold, cold water above the falls.
The view back as we started the descent was immense: Nevada in its entirety, and Liberty Cap looming above.
I highly recommend this hike! It's a great way to spend a day in Yosemite, especially if you're staying in the valley and you don't want to have to drive to your trailhead.