Well, given that I would only need a few million to live comfortably for the rest of my life without ever having to work, and probably having some left over to leave to my loved ones... I'd probably wind up investing a lot of that money into worthwhile projects to clean up seafront landscapes, and start revitalizing a number of neighborhoods that I think need attention.
As odd as it might sound given my right wing leanings, I do believe in charity, I just don't believe it should be mandatory. If I had THAT much money, WTF am I going to do with it is a good question.
Oh and perhaps most importantly, I'd probably put a couple of million away to gather interest and have myself cryogenically frozen, either before or after death, to be brought back when they could clone me a healthy body devoid of things like brain damage.
Investing in the space program might also be an option, since I do believe that way lies the future of humanity, but a lot would depend on who was in charge because with our leadership not taking it seriously I'd be concerned any money I donated would be siphoned for other causes.