Search on google
info: website url
Notice the search. Check if the domains are matching or not. And you'll get your answer.
Also, don't forget to check the drops of the domain. Dropped domains have a tendency to loose PR in google pr updates, although these updates are done on weekly basis now.
This is the best way. Go straight to the source.
As for tools the most reliable one I've found (that almost always corroborates the above source) is RankChecker.com - Check Fake PageRank (PR), Alexa, and SEO Details
So I'll check a bunch through that tool (most 4+ come out fake) and any of the real ones I'll verify the info:domain.com way
Or the SEOBOOK toolbar, I like it better.Fastest way to check page rank is to install the Google Toolbar (toolbar.google.com). It can be customized to take up minimal space, and fit nicely at the top of your browser.
This on is good too - http://pagerank.my-addr.com It can check list of domains and urls. Free version allows to check 40 urls form 1 ip per day.