What Is It?
Maltego is a program that can be used to determine the relationships and real world links between:
  People
  Groups of people (social networks)
  Companies
  Organizations
  Web sites
  Internet infrastructure such as:
  Domains
  DNS names
  Netblocks
  IP addresses
  Phrases
  Affiliations
  Documents and files
 
These entities are linked using open source intelligence.
Maltego is easy and quick to install - it uses Java, so it runs on Windows, Mac and Linux.
Maltego provides you with a graphical interface that makes seeing these relationships instant and accurate - making it possible to see hidden connections.
Using the graphical user interface (GUI) you can see relationships easily - even if they are three or four degrees of separation away.
Maltego is unique because it uses a powerful, flexible framework that makes customizing possible. As such, Maltego can be adapted to your own, unique requirements.


Who should use Maltego?
Maltego can be used for the information gathering phase of penetration testing making it possible for less experienced testers to work faster and more accurately.
Maltego has fantastic applications in:
  Forensic investigations
  Law enforcement
  Intelligence operations
  Identity fraud investigation
  Identity verification processes
 
In fact, Maltego can be used by anyone who manage inter-related information.

Maltego is accurate,fast and reliable. If access to "hidden" information determine your success, your company needs Maltego.

hxxp://www.paterva.com/web/Maltego/

(Thanks Mubix)

hope this is of some help

l8ter