I love Evernote. I use it for everything. Lesson plans, lesson schedules, notes, web clippings, lesson resources, travel notes and much more. I can access it on any computer and from my smartphone. I can even share notes and notebooks with other people (like my students). It is an indispensable app for me.

Evernote also has the Evernote Trunk. The Trunk has apps that integrate with Evernote, scanners that scan directly to Evernote, pens that record what you write and send it to Evernote, and much, much more. There's even one that allows you to save things from your Twitter and Facebook streams directly into Evernote.

If you use Evernote, this is definitely a site you should check out.

Related articles:
http://educationaltechnologyguy.blogspot.com/2009/06/evernote-free-online-notes-and-more.html 
http://educationaltechnologyguy.blogspot.com/2009/09/what-technology-i-use-on-daily-basis.html