If you do and you have a reasonable affiliate program on it, I run a 7000+ subscriber strong JavaScript newsletter and would be all over this ;-) (Same goes for any good JS related products, to be honest.)
I've never run one. But the best ones I'm an affiliate on so far seem to be http://zferral.com/ and http://clickbank.com/ - they're very different. Zferral is basically a webapp that lets you create an affiliate program for your "whatever" using your existing billing system. Clickbank, on the other hand, actually hosts your product and does payment processing and affiliate stuff all in one.
I know many people that would buy something like this. It sounds like it would be a great into to the basics of the main web technologies.
You mention a database - client side local storage or server side? If server side, what server side language were you planning on using, out of curiosity?
Server side. I'd probably pick one or more web frameworks with simple ORMs. Basically take RoR, ASP.NET MVC/EF, and PHP Hello World applications, and add one more models and a couple of pages.
It would include a full working website with database as a starter kit.
I wonder if something like this could be profitable...