Maltego is an open source intelligence and forensics application. It will offer you timous mining and gathering of information as well as the representation of this information in a easy to understand format. Coupled with its graphing libraries, Maltego allows you to identify key relationships between information and identify previously unknown relationships between them.
It can be utilised in searching for the following (entities):
* Autonomous System Number
* DNS Name
* Email Address
* IP Address
* MX Record
* NS Record
* Phone Number
It is offered in 2 editions which are Commercial edition and Community edition. Community edition can be downloaded from the following link:
It is also available as a built in tool with the current backtrack editions.
The following link describes in detail the process of finding information about people and organisations using Maltego in 2 parts.