While developing sites for web marketing company Leads You, I've developed SEO Links module. Its main purpose is to provide ability for centralized creating links with keywords. It work next way - you define list of keywords, URLs for these keywords and from now all node's content passed through SEO Links filter will be processed so all keywords will be replaced with links to appropriate site.

After you define new keywords:

You will see all filtered content with new links added to the filtered text:

It is universal solution for both nodes and blocks. While you use some input format which uses SEO Links filter you will get these links in the content. Nice way to provide backlinks with great anchor text =)

Module is for Drupal 5.x, and, possibly, has some security issues, as it was developed for non-community edited content. So use with care. I plan to polish it and contribute to Drupal community later. After this it will be possible to port to Drupal 6.

Here is link to download it: http://pavel.karoukin.us/sites/default/files/attachments/seo_links.zip_.txt

Your comments are appreciated!