FireFox
If you use Firefox (and in my opinion you should!) you will know about extensions. For those that don’t, these are simply add-ons to the Firefox browser that let you personalize your user experience.

Search Status
One of the most powerful extensions I use is Search Status. It provides you with handy information like PageRank, AlexaRank, backlinks, keyword density, link reports, whois and lots of other SEO related tools.

You can see how it simply sits in the bottom corner of my firefox browser next to my Alexa Toolbar.

Below is the context menu displayed when you right click the “q”symbol. You’ll notice how it allows you to highlight nofollow links, generate link reports, view your site’s meta tags, keyword density, show which pages are indexed and where your backlinks are coming from.

These are all extremely useful tools for monitoring your own site but here’s where it gets interesting…

Unfair Advantage
You could use it to find out which sites link to your competitors pages, view their traffic sources and perhaps see who their likely affiliates and JV partners are. This is also a good way to find new link directories and exchanges simply by viewing where your competitors go to place their links.

An unfair advantage? Possibly. Powerful stuff though I think you’ll agree.