Wonderful thing about Firefox extensions is the autoupdate feature. Go to Tools->Extensions, select Find update and for all installed extensions you get the latest and greatest .... usually.

One extension where the update did not work was the Del.icio.us button for Firefox. I was happily using version 1.2 of the plugin and would never found out about the update, if I had not set the new workstation. The latest version 1.5.29 did not show in the updates. Which is too bad, because it is so much better ...

New extension gives you new menu item and sidebar, with two panels: tags and bookmarks. The tags are interconnected, for example, if you have bookmark tagged as '3d' as well as 'animation', you will see animation as child of 3d tag as well as 3d as child of animation. Tags can be sorted by alphabet or by frequency, bookmarks by last added, site, most visited, last visited.

Complete tutorial is here. If you are still using the previous version, go ahead and upgrade - by uninstalling the old version and installing new from here. It is absolutely worth it.