I'm a big fan of the guys at SEOMoz, I spend a fair amount of time (perhaps too much) reading through their resources.
And, I love their tools. They have another one which will do a an assessment of how competitive a given phrase is which is pretty handy based on a lot of the same data for PageStrength.
There's another Firefox extension I like a lot from Aaron Wall at SEOBook which actually inserts various ranking data right into the Google and Yahoo SERP you can see IBL, DMOZ, Wikipedia and a bunch of other stats similar to those in the PageStrength tool.
As a newbie I can't link so: tools.seobook.com/firefox/seo-for-firefox.html.
And then finally, there's one from a company called Quirk which gives Google and Alexa persistently in the status bar of Firefox with a number of other analysis tools which I also have installed: quirk.biz/searchstatus
I could never find one though that worked for my target client - not many small business clients want to go to a bunch of different sites or install strange things.
So, instead of continuing to direct people to Marketeap, Google and Alexa I commissioned a tool that combined them all plus a DMOZ query and posted it on my site.