The plugins are released through dev.bukkit.org and can be browsed at http://www.curse.com/bukkit-plugins/minecraft
All the released/beta bukkit plugins can be found here: http://www.curse.com/bukkit-plugins/minecraft Edit: Damn! Ninja'd by eyamaz!
For a plugin page that is not cluttered: http://dev.bukkit.org/bukkit-plugins/ Which one you use is up to you, they both use the same system.