I have been using Evernote for a while now.
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at any time, from anywhere.
Now what I like about Evernote, is not only can you use it online from any web browser, they also have clients for OS X and Windows. If you have a Tablet PC you can even use your “Pen” to make notes too.
They also have a Windows Mobile client and one should also be available for the iPhone (and so the iPod touch) soon.
There is this video which helps explain things a little better.
Evernote was until yesterday an invite only site, it is now in public beta so anyone can now sign up.
Find out more.