Some websites I have found interesting (in no particular order):

Web Database Proposal — HTML5 proposal for a SQL interface to web databases similar to YQL. This would be awesome! Though it doesn’t really makes sense as a part of HTML5…

SVG-edit — In browser SVG editor. Give this another year and you will have no need for Inkscape.

3D CSS Visual Effects — Boy, those Webkit guys keep doing awesome things for CSS, don’t they?!

Javascript tests, compatibility tables and examples — Some compatibility tables on which browsers support some new javascript features. In particular look at the getters and setters section, that’s enough for me!

Augmenting photos with OSM — Overlaying roads and elevation gradients onto photos. I’m not sure what I would use this for, but it is really cool.

Building Rome in a Day — Recreating Rome (and other cities) from Flickr photos. Technology is so cool!