Ok, so I found this method out a few years back, as far as I know this is the first time anyone has disclosed this method. Its so simple you will kick yourself. Get a program called Xenu Link Sleuth - http://home.snafu.de/tilman/xenulink.html << thats the legit site, dont download it from anywhere else. Then you setup Xenu to crawl Dmoz.org - Now this can take days, so try targeting categories if you want a faster result. Once the scan stops. Any sites that returned an error are probably dropped. Or the webmaster has given up, stopped paying the hosting and will likely not be renewing the domain. Now this can help people in many ways. If your doing your own SEO you can snatch the domain and put up a blog feeding link juice to your main site. Or if you want you can go around the whole of dmoz, buying up all the domains and start selling niche links on various webmaster forums. Enjoy.