As presaged by Dave Winer yesterday and announced by him today, Ray Ozzie, now at Microsoft, has introduced Simple Sharing Extensions as a new XML nameSpace using RSS and OPML to allow lists of items, and outlines to interactively exchange their information. Marc Canter also hinted at this development in his guest piece for the AlwaysOn Network "Breaking the Web Wide Open".
I believe that this is going to be a tremendously important development, on several levels.
You can also find more information in the SSE FAQ. Don Dodge has a well-writtne piece on SSE. There's an interesting preview on the AttentionTrust Blog, as well.
Update: Mike Arrington says
"New companies will be built on the back of SSE."
-- Michael Arrington "COOL - SSE turns RSS bidirectional"
Update 2: Alex Barnett has a good list of reactions to the SSE in his post, "Microsoft proposal: Simple Sharing Extensions for RSS and OPML".
As Miss Rogue points out, the blogoshpere is abuzz about gada.be, the search aggregator, primarily for mobile devices, but available from any platform, that uses RSS and outputs through OPML. So much so, that you can't get to the site.
We started getting referrer stats from opml.gada.be yesterday, and, as I mentioned in a comment to Gee-Gada.be, I could get to that URL, but no other.
I finally got through to teleinteractive.gada.be [hey, this is all about hubris after all]. The results were all about, well, us. Except for one for teleinteractive audio by Rohr Post. There were no results on CASTLE - Computer Aided System for
Teleinteractive Learning in Environmental Monitoring, which surprised me.
Gada.Be looks like an interesting system. Though I've never have had trouble using search tools on my Palm via Bluetooth to my mobile to the Web. But having searches from multiple engines as RSS feeds into my aggregators is really cool.
I recently posted about Categories for news feeds and blogging, in relation to suggesting additional categories for Bayosphere Citizen Journalists' articles and for organizing the RSS, RDF or Atom feeds to which one might subscribe in a feed reader. You can read the original post in either the TeleInterActive Lifestyle or Bayosphere. Steven Livingstone-Perez responded, via trackback, in taghop: Managing Categories
Joseph A. di Paolantonio recently blogged how he re-organized his categories to use technorati tags and is hoping to move toward a better fine-tuned folksonomy.
While i belive this is useful, I still see a few factors that I hope taghop.ORG can address when looking to perform such an activity.
-- StevenR2 in taghop: Managing Categories
So, I've spent some time since I saw Steven's response reading about Taghop, both in the COM and ORG domains. I created a Taghop account and added some URLs, for blogs from the TeleInterActive Press and Bayosphere, and used some of the "public" URLs for various news organizations. Taghop allows one to relate the tags/categories to others' tags or categories, and allows one to do so regardless of where one uses those tags, such as de.licio.us. So, Taghop was the impetus that I needed to create a del.icio.us account. 
I'm still getting the feel for things at Taghop, and Taghop is in beta. Perhaps Steven can answer some questions for me, and please don't read anything below as a criticism.
Steven, Taghop looks like an interesting project/product/service. Perhaps you could help us understand Taghop better, and answer my questions, via a post on your blog, with a tracback here. I look forward to conversing with you.