I purchased the SEO Booster PRO WP Plugin from Cleverplugins earlier today and I am very happy with it so far - in fact it is quickly becoming my favorite plugin.
I have it running on Dimensions Guide for now and it tells me a lot about my site on the control panel side and on the user side of the site it makes links to posts on the site based on the incoming searches.
You can see that on the bottom right side, the links there are automatically generated from SEO Booster PRO. There are a few other plugins doing this on the market but this one wipes the floor with them.
The plugin goes out to Google when you get a search engine visitor and checks you ranking for that keyword, and then decides if the key phrase needs some link love according to your settings.
I set mine to #4 - #20 so any search that comes in from Google with a keyword ranking from #4 to #20 gets a link (well up to the max limit you set - I set mine to 35)
That is really cool and helps your ranking on these keywords a lot
On the admin side it shows you live information about your searach engine visitors, and you can export this data to Excel and play around with it there.
Check them out here: http://cleverplugins.com/ (not affiliate link - I just like their product, so I am not writing this small review for profit )
They say on their site that you need PHP5 but I am running mine fine on a PHP4 server.