This summer, when we entered Yosemite to hike the John Muir Trail, we bought a one year park pass, with the intention of trying to go up there all four seasons. I've only ever been in the Summer, when it's gorgeous, but also has crowds that rival Times Square.
We headed back up there for my birthday at the end of October for our Fall trip. It was fantastic. The weather was great, and there were no people around to speak of. We hiked what normally would have been a very crowded trail (Pohono) and had it all to ourselves almost all the way to Glacier Point. We camped just above Bridalveil Creek, which would have been overrun in the Summer.
I can't wait for Winter.(click images to embiggen)