http://www.onseo.com/forums/forumdisplay.php?f=17 All these TOOLS found for this topic are FREE - amazing
http://basicstat.com/ very helpful new tool that gives the current real-time info There are others that do the same thing - including Sitemeter.com I likes that
http://www.faganfinder.com/ So-o-o-o-o-o-o-o much good info http://www.copyscape.com/ who stole ANYTHING from my site?
This is a great tool because keyword density can vary per niche. Knowing what all the competitors for you niche in the serps on page one is great for creating your own content. Here is an article I wrote a while back that explains this ... http://www.seojam.com/search-engine-keyword-optimization/