I've got a tree on ancestry.com. Actually, I have several, because I've been tracing the parentage of the women I'm researching for my thesis and using the census and social security data to verify things like birth and death dates, number of siblings, immigration status, etc. It's a neat tool, and I recommend it to anyone interested in genealogy.
I went together with a friend and we're splitting a paid account. It's kind of neat to be able to log in and see what she's done to her family this week. We're both apparently a little inbred so we like to give each other a hard time about our familiy trees being more like wreaths. I haven't found any famous relatives this century, but my mother is a Trumbull in the direct line of Jonathan Trumbull, the revolutionary war hero, and his grandson (I think?), also Jonathan Trumbull, who has a painting depicting the signing of the declaration of independence hanging in the Smithsonian. We are also related by marriage to George Washington via Jonathan Trumbull's son.
My Dad's side is pretty sketchy considering that everyone past my grandparents were born in Poland. But I have a fourth cousin in Warsaw who has done a really great job of collecting data on them. I haven't entered it into Ancestry yet but when I do I bet I find a lot of neat stuff. I've been working on Mom's side first because it's easier.