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?!
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!