A links directory is one or more pages listing links to web sites. A good quality links directory can be a treasure trove to someone, which they will promote for you to all their friends.
The trouble is, what's the best way to maintain the links directory? What if links go stale? How do you detect it?
Site Bar (sitebar.org) -- is primarily focused on managing bookmarks. While web browsers offer bookmark facilities, it can be clumsy especially if you use different computers from time to time. And how do you move your bookmarks from one computer to another when you buy a new one? The solution sitebar.org offers is to store your bookmarks on a server computer somewhere. They offer several ways to integrate those bookmarks with the web browser, and you can access the bookmarks from multiple browsers. You can also publish the bookmarks publicly, and use the public bookmarks on your own website.
de.lirio.us and del.icio.us -- These are both "social bookmarking" web sites. People register with the web site, and can easily post to the site web bookmarks. All the bookmarks are public, and the most interesting thing is each one is "tagged". The tags are meant to help categorize the resources. The links can be accessed programmatically for republishing elsewhere. (http://search.cpan.org/dist/Rubric/: is the source code for de.lirio.us) (If you use Drupal, the del.icio.us module can import a set of bookmarks and display them on the drupal site)
Cute Marks -- Is an open source bookmarks manager you can install on your own server.
FaniBook -- is a shared bookmarks manager allowing a group to collaboratively build a links directory.
Gentleware's Bookmark manager -- Link Manager can be used as link section of a website or a personal bookmark manager. You can publish your links/bookmarks or hide them behind a login. It is implemented in PHP.
Bookmark manager -- is a online bookmark manager, it is meant as a replacement for a browser's bookmark system. It is implemented in Java.
Online bookmarks manager -- This is software that lets you access, manage, organize, and share your personal bookmarks through a web-based interface. Ol'Bookmarks is highly customizable with multi-user and themes support.