I think I mentioned I've been revisiting calculus, just to keep the blood flowing to the old noggin, and I've seen a lot of resources out there, everything from books to classes on the web.
The most intriguing resource I've run into so far is Karl The Tutor.
I don't know Karl or anything about him. I don't know if he's a real person or a group of people, I don't know how old he is, if he's really a he, or even what country he posts from. All I know about Karl is what I see when I link to his site. And he interests me.
In the first place, I like his approach to math. It works for me. Makes me feel good about spending time with calculus.
But, beyond that, his business model fires my imagination. How does he do it? I wonder. I don't see any ads or other obvious source of revenue, but the site looks a little more industrial strength than the kind of hobby sites like The Hive that you find on Blogger. Is Karl independently wealthy? Is he a tenured math professor with a little time on his hands? Is he funded by an elite group of intellectuals who want to foist their particular view of calculus off on the world? Or is he selling something that I'll find out about later, once I'm hooked on his site? I don't know.
And, because I don't know, I can make Karl up any way I want to. And here's how I see him.
I figure Karl is a guy whose greed is under control. What he wants is a way to make a living doing what he loves to do, teaching calculus. He doesn't waste his time trying to make more money out of his site than he needs for a comfortable living. He'd rather spend that time teaching math. So he sets up a not for profit, gets some grants and pays himself a reasonable salary. Throw in some money to maintain the site and maybe take a trip to a good conference now and then, and you have it.
At my age, that's a model that appeals to me.