One of the biggest items on my bucket list is to visit all of the U.S. National Parks at some point in my life. A secondary goal is to make it to as many of the State Parks and National Forests as possible, but that starts to stretch the list considerably. Still do-able, I'm sure, but a bit more intimidating to think about.
I've already seen a handful of the Nationals on various family vacations and such, but I would love to not only make it back to the ones I saw when I was younger (read: didn't appreciate), but to cross each one off that I have yet to experience. According to Wikipedia, there are 58 national parks in the States. Some of these will be easy to get to - the Shenandoahs are practically in my back yard. Some of them will take a bit more planning and saving (US Virgin Islands and American Samoa, I'm looking at you!). But over the course of my life, I hope to experience each and every one of them.