WeaverDetect shows you exactly what theme, stacks and plugins a specific site is using!
To install, drag the below bookmarklet to your browser bookmarks bar. Then, when you're on a page you'd like to analyze, simply click the button for instant results.
It's also possible to use this service without the bookmarklet; say you want to view the results for http://www.example.com
Simply prepend the URL with weaveraddons.com so that the URL becomes http://weaveraddons.com/http://www.example.com
Now hit the ENTER key, and the results will be displayed. Easy!