Rated 5 out of 5 stars

Of course for security reasons it's best to download 1.2.0 and hack it yourself to work with Firefox 3, but I've made a hacked version available on the web here:

http://msittig.wubi.org/test/del.icio.us-1.2-fx.xpi

Use it at your own risk, but so far it has worked fine for me.