Is there a piece of software out there that can tell me what framework or CMS was used to build a particular site? I'm thinking there might be something that can look at the way a page is formatted and deduce what, if any, framework or CMS was used to generate it.
It's doubtful you'll find a tool that can identify the CMS behind any site, if only because it's possible to hide most of them if you're determined enough and some even make it easy.
Wappalyzer can be installed as a plugin for Firefox or Safari, and also offers a bookmarklet version at bottom of the install page.
There's a Windows application called CyberMake that seems primarily intended for keyword research which claims it can identify an extensive list of applications. But it seems sketchy to me for several reasons you can figure out yourself if you decide to search for it.