Fluttr lets you easily keep track of todo items. All you have to do is remember what url you choose. Keep it secret or share to have a collaborative todo list.
I'm learning Rails and Javascript so this has been my first good experiment. Took me just a couple of hours to put this together and I'd love to hear what you think!
However, (oh I hate to say this) there are a bazillion todo apps out there. Every programmer must have made one.
I know you made this for learning. So, what I'd suggest is you take the same code and turn it into something more fun. Have a look at http://www.thathigh.com/. Technically, it's similar to your site, but it's a very viral social app, which people love.
Good luck with your experiments!
This on the other hand is a to-do list. Yes its pretty simple, but sometimes simplicity is elegance.