simplenoteapp.com is a pretty cool application for notes. For the registration you need just your E-Mail address and a password. After them you can create notes in the web application. But there are also many mobile devices and desktop devices to access your notes on the simplenoteapp server. There are apps for iPhone, iPad, Adroid, Widgets for Mac and desktop apps for Mac & Windows.
You can edit your notes on every device and the app synchronizes it transparently. It is like dropbox for notes. You just add a note on your Adroid phone and a view second later it appears on your Mac OS X Desktop.
There is also a version control feature. All your changes to one notes are tracked. If you want you can go back in the time line and see the status of a notes before a view days. That is pretty awesome.