Evernote - capture anything , save your ideas , and access your information from anywhere using either a computer, or a phone and mobile devices.
GumNotes - stick notes to your documents, websites, gmail, etc.
My School Notebook - easily write your notes to a computer or phone, edit and format them or insert an image or a video into them.
Springpad - much like Evernote. Quickly save anything you want to remember.