AutoLink provides users with a way of creating a list of "hot words." Whenever these words appear in a post, they are automatically linked to a designated URL.
For example, if you were to frequently write about Movable Type, and anytime you mention the phrase "Movable Type" in a post you want it to be linked to http://www.movabletype.org/ without having to enter the link manually. This plugin will do that for you.
More advanced users could use AutoLink to set up linking rules that will turn Wiki formatted words into links into their internal/external wiki.
Movable Type versions: 4.3