An excellent paper written by the author of Vi, Bill Joy

The Bvi editor is a display-oriented editor for binary files, based on the Vi text editor.

Basic equivalent Emacs editor commands and operations for users of the Vi editor.

Tutorial based on the graphical cheat sheet created for people learning Vi or Vim.

Free Notepad replacement highly compatible with the Vi editor issued under the GPL license.

A getting started guide for Vi users.

Nvi is an implementation of the Ex/Vi text editor originally distributed as part of the Fourth Berkeley Software Distribution (4BSD).

The homepage of a popular Vi clone available for many operating systems.

BSD ex/vi 3.7 ported to modern Unix systems. The original Vi source code, with a few necessary modernizations.

Overview covering history, versions of Vi, manuals, FAQs and other sites of interest.