This is great post by Stevey Drunken about mastering Emacs text editor which is quite quite popular among UNIX hackers, computer programmers and power users:
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Emacs is the world's best text editor. It's not just the best for editing program source; it's the best for any kind of text-editing. Mastering Emacs will make you more effective at writing and editing email, documentation drafts, blogs, HTML pages, XML files, and virtually everything else that requires any typing.
The tips in this little document are geared towards Emacs power-users. You should be familiar with the basics of launching and editing with Emacs, and you should already know the essentials of copying stuff into your .emacs file, and debugging things (or finding a friendly Emacs Wizard) when something goes wrong.