I just finished a nice little plug-in for GreaseMonkey which changes all of the 'Email' links in News Gator Online to del.icio.us post links, which is much more useful.

More information about the code can be found here: DeliciousGator. Give it a try and let me know if you notice any bugs. The only sticky point, currently, is that in order to configure any of the options, you have to download the javascript file, edit the options, then place it somewhere so that Firefox can get to it - not terribly convenient. I'm hoping that some advanced configuration options come out soon.