Addthis is a great way to make a website look fancy without doing much work. In the most simple of senses it is a bookmarklet that will transport the page you are looking at to a huge stack of different web based services. Stuff like Delicious, FURL, Facebook etc. The extra bonus is that there is no cost involved and setup doesn't take very long. If you've been developing in a CMS or with a consistent template system it should be a trivial task.
Since Dspace is my most current project I thought it would be a good idea to include the Addthis button to that as well. Now Dspace is a bit of a bear when it comes to rendering pages so it won't be as straight forward as with a PHP or HTML site.