What Are Those Funny Little Bookmark Boxes Everywhere
You will have probably noticed that many of my pages have one or more graphics looking like:
These buttons are a simplified interface into social bookmarking (if you don't know what that is, try reading my blog entry on social bookmarking - this page also has a good description). Each social bookmarking site has its icon and its own unique way of integrating your site with it. This leads to pages that can literally have dozens of similar looking "add this" buttons on the page, one for each such site. AddThis.com provides a single button that takes you to a page that allows you to select the social bookmarking site you prefer and then will add the bookmark to it.
AddThis has two major advantages. First, I don't have to keep updating my site with new bookmark buttons and deleting old ones as new sites wax and wain in popularity. Second, you don't have to look at all of those ugly buttons when you probably care about no more than one of them. Here is one set of buttons I found on a page I was looking at:

The only real disadvantage I see to AddThis is that it is two clicks to get to your bookmark site rather than one. Not much of a price to pay in my mind. But if you consistently use the same bookmark site, you can check a button on AddThis to tell it to so and then it will not show you the bookmark site chooser window again.
One really nice feature of AddThis is that it also allows you to add the bookmark to your browser. So, if you you prefer to bookmark pages by clicking on buttons on the page rather than using your browser's controls, you can use the AddThis button.