There're some great ideas here!
I wasn't quite thinking of fleets of jets and yachts when I posed the question, but I did say money was no object, and I can't say I wouldn't be interested in flying some of the smaller end jets as a hobby. If the Maverick Jet mob ever get their act together, their single seat jet would certainly be an interesting proposition!
I was recently watch an American show called Working on the Railroad, on the How-To Channel. Some of the model train layouts they show-cased were truly awesome in size and detail. I must admit to occasionally thinking that if I had the time, money and space, I'd like to do something similar. Of course, if I got really rich and keen, I could use my hobby machine shop (see opening entry on this thread) to create Live Steam Engines and get involved with the local Live Steamers club.