Link Monitor is a FREE WordPress plugin that will help you to hide URLs from posts/pages and comments.

This plugin hide links to articles published by members of Spain's newspaper association with AEDE and CEDRO. Link Shield is a Must-have plugin

External Links Mask add a Out links section in your WP ADMIN and mask all external links in post content.

This plugin allows admin to customize the admin bar and much more.

Closure of external links from indexing using jQuery script.