Whatweb identifies websites. its goal is to answer the question, "what is that website?".
Nmmapper provides dns lookup tool to let you check all dns records of a domain.
Raccoon is a tool made for reconnaissance and information gathering with an emphasis on simplicity.
cmseek is a cms detection and exploitation tool,capable of scanning numerous content management systems.
Web application firewall detection discover the security protecting your target.
Dns reconnaissance is part of the information gather stage of penetration testing.