Zettels is "a personal web memo note box." They say: "This is not a software for local installation but an internet service. The access to your note box is restricted to your own private use. There is no public area accessible by other users of Zettels. Your privacy will be maintained. The connection from your browser over the internet to your note box at Zettels is "SSL" encrypted. In this way we ensure that only you have access to your memo note box."
I have looked at it many times, but I have never signed up. Looks interesting, though.