In October, 1997 Loretta and I went to Yosemite National Park on a mini-vacation. We spent four days there, driving up on a Thursday afternoon and returning Sunday evening. We stayed at the Yosemite Lodge, which is a hotel on the main valley floor. It's not the most inexpensive place, but very convenient for sight-seeing.
We went on a few of the organized sight seeing tours, and spent some time just walking around as well.
Overall, it was pretty nice.