If you're looking for more desktop-style layouts, I'd recommend checking out AlloyUI (http://alloyui.com/), which builds on top of YUI3. They've been doing a lot of great work there.
On emerging standards, we're definitely taking a look at those, we have a few Gallery modules (our user-contributed modules, which can be approved to be placed on the Yahoo! CDN) that do act as polyfills for several of the new emerging standard elements.
I don't remember offhand if we have some for XBL or Shadow DOM yet, but I definitely know that we had a module for X-Tag [1] a while back. I'll definitely check it out, and get back to you on the rest.
On emerging standards, we're definitely taking a look at those, we have a few Gallery modules (our user-contributed modules, which can be approved to be placed on the Yahoo! CDN) that do act as polyfills for several of the new emerging standard elements.
I don't remember offhand if we have some for XBL or Shadow DOM yet, but I definitely know that we had a module for X-Tag [1] a while back. I'll definitely check it out, and get back to you on the rest.
[1]: http://www.x-tags.org/