vim autocomplete, or really, autoexpand abbreviations
All about shortcuts as well as abbreviations: http://www.linux.com/archive/articles/54936
To set abbreviations only for insert mode (which seems a little safer) add to your .vimrc file (or in Agaric's case, an included .vimrc-agaric file with all our Drupal and other development-specific additions) abbreviations in the format iab abbr abbreviation
.