A couple of days back I created a Firefox toolbar for my blog as an experiment in learning XUL. The toolbar is shown below. You can install the same from here.
Now you can create a toolbar for your own blog or site. The source for the toolbar can be downloaded from below after which you can edit the code to suit your site; to help you there is a nice reference for XUL elements here. The idea for the post was inspired by david.
Downloads : [downloadcounter(codedieselToolbar)] / File size : [downloadsize(codedieselToolbar)]