WordPress plugin : wp-link

The WP Link Directory is the first and the only one link directory plugin on the Internet for WordPress admin to store and maintain a set of links in classified categories. Useful for building content and getting other webmasters involved in your site’s content development.

Full Features:

* Creation of link categories, sub-categories with descriptions
You can create any number of categories with description in the directory, including sub-categories.
* Quick add of link from admin backend and visitor front-end
visitors will be able to click on this link “Insert your link here”, it will pop out a form below for submission. Clean and simple.
* Search engine for admin to find link
You can search for a particular link based on its title, domain name, email address, etc, thus never have to worry about can’t find a link that you want to delete or edit.
* Easy integration to your WordPress theme
* Backlink cleansing for checking reciprocal links : process that checks each reciprocal links and see if the site is linking back to you as it promised. A list of broken links will be listed and you can either remove them or do something else.
* Email notification templates allows you to set a custom email template system for link notification and approval.
*  SEO friendly URL rewrite feature, re-writes all url to search engine friendly format

more @ http://www.alectang.com/wordpress-link-directory