Have you ever come across a really cool site and wondered what technology they used to roll it? Does it support RSS, what do they use for Web Metrics, which Ajax library are they using, what server platform have the selected, DO they have a P3P policy?

Well, wonder no longer... just visit BuiltWith, tap in the URL and they'll deliver a wealth of information about the site you're interested in - along with a measure of what %age of their surveyed base is using the same technologies.

At the moment it's fairly new so the %age of people using a particular technology might be skewed but it's interesting to see how some of the apparently popular services are not scoring so well just yet... time will tell though.

Check out their blog for news of new releases and to discuss suggestions to improve it... though as it seems to do just what it says straight out of the can I can't think of anything I'd like to add at first glance (rare I know!)