OpenLinkProfiler.org is a free tool, while WebMeUp.com is also currently free but they may charge in the future. This adds to the current tools in the market, including Majestic SEO, Ahrefs, Moz, Open Site Explorer and of course, Microsoft’s Bing Webmaster Tools and Google Webmaster Tools.
OpenLinkProfiler.org, since it is free, and we have not covered it before, offers:
Which is the best tool? Hard to say, you should play with them, and do your own analysis. When it comes to finding new sources of links, as well as monitoring your own links for “negative SEO” reasons, these link tools have become more and more value to the SEO toolkit.