Linker is a plugin which automatically places links on pieces of text of your choice in your Joomla! articles. You may use it with a simple text expression or a more advanced perl regular expression.
Linker is in current version port of Pluglink (http://archive.extensions.joomla.org/extensions/edition/replace/9094) source to Joomla 3.0 .
So most credits belong to author of Pluglink Alexandre Huber (http://www.moleculargeek.net/pluglink.html).