I've incorporated the service provided by into this blog. I've noticed a few blogs using it and have found it quite useful. Donal gets the privilege of being the actual source of the service for me, until I checked tonight I had always assumed it was just another Wordpress only goody.
Snap is a great feature anyway. Basically it gives you a little popup preview of the external webpage, when you hover over the associated hyperlink. Try it here now! I found it very useful as I am sometimes reluctant to click away from a body of text. I think it will be really handy for referencing images in posts.