I was just checking out the maltego website and their new product to see what it was capable of. For a preview check out this video Maltego Episode 3as you can see this could be an incredibly useful tool for seo research.
Maltego is a commercial software but if you get the beta release of backtrack4 (linux pentesting distribution) you can use the maltego software.
Definitely work checking out for a very reliable alternative to many paid tools.
edit* A community version of this software can be downloaded and used for free on win platform.
edit* just thought I would throw in some information from the maltego site