You may have hated him at Microsoft, or have loved him. But after working 30-Years in Microsoft, Bill Gates (Wiki, Official Bio from Microsoft, Bio at Gates Foundation) is now working full-time in the Gates Foundation, along with his wife Melinda Gates. Inspired by Warren Buffet and his Annual Letter to Shareholders, Bill Gates has decided to do the same.
It is an excellent read. It is quite long. You can either read it here online, or download it here (20 Pages, 4.6MB PDF). If nothing else, it will give you some form of semblance as to what Bill Gates has decided to do with his life – work for humanity.