Snap gives you a high quality link preview so you can easily decide if a site looks interesting enough to fully load. 
Plugoo enables you to chat directly from your Instant Messenger with any visitor of your blog. You use the plugoo on the side bar as your IM window. 
Twitter is kinda like a blog within a blog. Sometimes your not doing anything interesting enough to warrant an actual entry, but you might want to keep any stalkers up-to-date with what/who your currently doing/thinking/having sex with. 
MyBlogLog is a cool way to interact with others in the blogosphere. The little widget shows you who recently visited your site and may help drive traffic to your site, but it's too soon for me to tell if it's working.
Flickr widget shows a mini version of your already uploaded images. Clicking on one of the mini images will take you directly to that image. So there's my list. Does anyone know of some other cool widgets? Think I have too many?
