AddThis toolbar

[Gar]

http://www.addthis.com/

I haven't seen this mentioned here yet, it's kind of a handy thing to have on your site.  It adds a row of buttons that make it easy for people to share it on Facebook and Twitter and the like

[Alectric]

Around here we seem to be in favor of the Sociable plugin.  Personally, I don't like the AddThis toolbar because if I hover over it, even by accident, my browser freezes up for like 15 seconds until the expanded menu appears.  At least when it's the default style.

[Miluette]

I like AddThis, but I may opt for an alternative soon, as it seems to pull up its popup even when I don't hover over the button sometimes. It also causes a little gap to appear at the top of whatever page it's on. It took forever to find that out, and it's annoying as hell.