Before I've even had the chance to play with Microsoft's Simple Sharing Extensions, Ray Ozzie just shared a prototype they have been playing with internally. Its called Live Clipboard and basiclly is a clipboard for the semantic web.
Honestly when I first read the post, I did think this would be perfect as a Firefox Extension or even Greasemonkey script but you would miss out on the desktop side of things. I'll be interested to know how flexable Live clipboard is. For example will it read all types of Microformats? How about FOAF and XFN? Humm, I wonder if you could do something between a Firefox extension and a Yahoo Widget?