I just came across an incredible relationship mapping tool which determines website relationships via either Keywords or URLs as seen by Google. The tool itself is simple enough, programmed in Java and presented in a very neat looking web 2.0 type of structure. However, the information which it presents is incredibly insightful and very very useful.Now having a relationship graph drawn out for a website is nothing new and we have seen many widgets do it without much difficulty. However the Touch Graph Google website relationship tool can actually show you relationship of websites which are directly related (parent company website, associate websites and affiliate websites) as well as indirectly related, such as an industry competitor whom you do not link to.
This gives you two very big advantages, the first being that you can see if your website and the websites which are related to you are within the same topical neighborhood. Secondly, you can find competitors you have never ever heard of and then drill deeper into their architecture and their relationships (obviously to discover potential link building opportunities as well as keyword research *ahem spying*). Adding to this, it also gives you an insight of what Google can determine without the helps of links on a website about their topical neighborhood.
Regardless, this tool is definitely worth a try even if you know another tool that does the same thing, since its free and its spiffy, so check out the Touch Graph Google relationship mapper.