Erik D. Jones's Blog

Maltego calls itself an “open source intelligence and forensics application”.  Basically it uses “transformations” or heuristics to derive relationships between entities and extract data from discovered data.  In short, it is a highly configurable crawler that will find related and connected data points based on several different types of starting nodes that you can seed such as: ip address, person, phone number, etc.

Quick start guide:

0) Download the community edition.
1) Add a person entity and, using the properties pane on the right, enter a full name.
2) Right click on the newly created entity and select a transformation to run such as “Email addresses” or “Websites and Blogs”.
3) Watch your graph and data grow!

Check it out by visiting Maltego’s website.

Thanks to Mubix for the original post.