Yesterday a new Google Chrome extension named Kuber PageRank Checker was released which allows the user to view the pagerank of webpages beside the address box. Apart from that you can also check the Alexa rank and WHOIS information in your Chrome browser itself.
This is a handy SEO tool which enables the user to get full information about the site’s authenticity and value . If the PageRank of the page in current tab is not available, the tool shows the PageRank of the domain instead, prefixed with ‘S’.  The PageRank value is cached locally, so it doesn’t have to hit the server every time you switch tab. Moreover, click the icon Alexa rank of the site is displayed in dropdown, as well as links-in number and WHOIS check link. Below is the direct link to the official Google chrome extension page
Kuber PageRank Checker – 1.0.0
P.S :- The extension is only meant for Developer Builds of Google Chrome 4.0+ Since the application is in beta mode you may experience some errors.