I love the web. The web should allow anyone to access any experience that they need without the need for native install or content walled garden.
I've added hCard, a microformat, to my blog. It makes my contact info machine-readable while still being visible to readers. It's basically an XHTML version of the vCard standard. I'm not totally sure I implemented it perfectly with the DIVs and spans, but check out the hCard creator tool if you're interested.
I just discovered the Technorati Tagger application (http://www.ultraseeker.com/tagbuilder). It's decent, converting user-generated tags into XHTML. This represents the simpler half of what I'm aiming to build in my upcoming AJAX application.