Linkscape has always been a project with a lot of promise. Building a crawl of the WWW that can expose link data in interesting ways, calculating metrics in the ways search engines do and surfacing potential SEO opportunities are all a part of that, but it's a lot of work and time to get all the potential functionalities into real-life tools. Last week, Linkscape took a giant leap forward in usefulness with Nick's new Competitive Link Finder.

Here's how it works:

1. Takes a pair of inputs - your website and the websites of 2-5 competing sites (or sites in the same sector)
2. Uses a link graph of 443 Billion Links to find link intersects between those pages (URLs that have links to 2+ of the sites you've entered but may not have links to your site)
3. Exposes a list of domains, with each linking page underneath along with metrics about those pages and sites.

Getting started is really simple. Just enter your own site, plus up to 5 competitors and the tool will find pages on the web that point to two or more of those pages, then list those in descending order of importance. The tool currently lives inside our SEOmoz Labs (which houses a ton of our best stuff) at https://moz.rankious.com/_moz/labs/link-intersect. We don't have fancy graphics or great UI in Labs, but the functionality takes center stage:

The results look like this:

For each domain that's mentioned, you can see a breakout list of the pages that point to those URLs, a checkmark next to the domains you've already earned a link from and data on the importance of the domains and pages (Domain mozRank and mozRank, respectively) listed. When you click the number of links from any given site, the tool surfaces a list of those exact pages, making it easy to see where and how they've earned those links. The features are just killer:

• The tool ignores nofollow links, so you're only seeing pages that have actual, live links to at least two of your competitors
• As our metrics (DmR, mR, DmT, etc.) have improved over time, the results really do feel like they're ranked in order of importance/potential value
• The data is extremely comprehensive - since Linkscape crawls a dramatic portion of the "important" web, the probability of finding great links is very high
• When SEOs talk about "hubs" from the Hubs & Authorities link model of the web, that's exactly what this tool is finding. Thus, you may see even more benefit from attaining these links than the raw metrics might indicate
• The tool includes pagination, so you can see hundreds, sometimes thousands of potential link sources and every new competitor or site you add is a new opportunity to discover more link resources
• Don't just limit yourself to narrow competitors - plug in any site in your field that's roughly related and you can find the intersection of potential links; the possibilities for finding links with this tool are limited only by your ability to plug in new sites and pages

The Competitive Link Finder is currently available only to PRO members (who have unlimited access for now). However, tonight, we're opening the link finder to all SEOmoz members; just log in to your account and for the next 24 hours (until 11:55pm Pacific, Thursday September 2nd) you can try out the tool yourself.

QUICK WARNING: We haven't exposed this much Linkscape data to so many people in the past, so things may slow down a bit. If you're finding the tool takes a few minutes to run, don't panic - the web is really, really big, so it's a bit complex to run data calculations like this :-)

I'm a fairly tough critic, but I have to say that every time I've used this tool myself or shown it off in the last few weeks, people have been incredibly impressed. Nick, Sarah and I spent the latter half of last week on Sand Hill Road pitching VCs, and I can honestly say that even they were really, really amazed by how high quality and useful the results are. Link building is, according to most SEOs, the hardest task we collectively engage in. I think the work here from Nick (built on the backbone of Linkscape that he and Ben developed) is finally making that process an order of magnitude more do-able.

p.s. I'd like to call out some of the other tools on the web which also leverage the concepts of link intersection. While I'm a personal fan of this one, there are some other good resources for those seeking link co-occurrence. The first tool of this variety used link data from a number of search engines back in the 1990's (I believe it was operated under WebsiteGarage which shut down in 2002). Jim Boykin's WeBuildPages also featured a free tool that used Yahoo! link data (now available under their Ninjas program), as did the software package WebCEO (though it appears to no longer be included). SEOBook (of which I'm a big fan) also released a Hub Finder tool in 2005, which was almost certainly the best iteration to date (note: I'm a paying member at SEOBook). Like Newton, we've been very lucky to see far by standing on the shoulders of giants, and I remain indebted to the terrific community around the SEO world.

p.p.s. Sadly, we've had to turn off access, but more than 30,000 reports have been run just today! If you'd like to try the tool, PRO is the way to go.