A very popular script for categorizing of links. This directory script has been used by thousands of websites on the Internet and is currently one of the most famous. It is also known for it's reliably and stability for handling huge number of listings as well as being a very Search Engine Friendly script. They offer two versions, one free while the newer version with more features is a paid software. And you need to pay for support as well. PHPLinkDirectory provides it's support in it's forums. Not only that, free mods and themes are available there as well.

PHP Link Directory

phpMyDirectory (Phpmd) is a vey powerful and secure directory script. It is primarily used for business directories. This enterprise strength script has a lot of features not found in any other script. Phpmd is writen in PHP and uses the database MySQL. Unique features include the abliltiy to generate a pdf version of the directory, allows users to network among themselves through personal messages and a full ad banner management system. There are also various modifications available by third parties. Phpmd provides support through email and a ticket system.

phpMyDirectory

eSyndiCat is a powerful directory script with a difference. Other than the regular features of a directory, it allows users to do link exchanges with each other by allowing it's users to request link exchanges. It also displays Alexa stats and PageRank. They offer a free and a "pro" version. The "pro" version cost US$49 per domain. This paid version allows link comments to be made by users and even enables the administrator to add or change link fields! eSyndiCat provides support through direct email or you can ask questions in the forums.

eSyndiCat