SpiderFoot is a free, open-source, domain foot-printing tool. Given one or multiple domain names. It will scrape the websites on that domain, as well as search Google, Netcraft, Whois and DNS to build up information like:
* Subdomains
* Affiliates
* Web server versions
* Users (i.e. /~user)
* Similar domains
* Email addresses
* Netblocks
SpiderFoot is 100% written in C# and is GPL licensed.