- HighlightingCompletion? is a variant on completion in Emacs. When typing in the minibuffer (for example), whenever the text can be completed, the completion is added to the minibuffer provisionally--it is more a visual cue as to what would be inserted if you hit the TAB key than anything else.
- LightningCompletion is an improvement on whatever completion Emacs does already; it incorporates ``dynamic completion: completion without having to hit the TAB key or anything else. This is very useful when added to commands like find-file or switch-to-buffer or describe-lisp-function.
- UltraTexMode is a major mode for typing TeX documents; one of its main features is dynamic completion on TeX commands. It has a few other nice bells and whistles. (This includes the lightning completion package, by the way.)
- LaTeXSymbols provides commands in XEmacs to open up windows with tables of various sorts of symbols. Here is an example of this.