It’ll be in Emacs 22, but the Organizer Of The Future is here today and works with GNU Emacs 21 and XEmacs.
Emacs Org Mode is for taking notes and organizing thoughts. I find it excellent for rapid note-taking. It supports HTML, plain text, iCal, or LaTeX export, a Markdown-like markup system, and simple links. It also has the best Emacs table editor I’ve ever seen. This is amazingly good elisp. This was the missing feature for me to take notes during many meetings.