PR as in the gren bar that you see is a complete waste of time, better to check backlinks via the various firefox plugins available SEO Book is my favorite.
Google's stated Pagerank is only one of over 200 metrics by which they rank a site. This is why they've stopped updating it as frequently to push the point that just because it's measurable doesn't mean you should put so much stock in high pr backlinks. Better to provide such good content that it draws you those links.
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Online you will get lot of software tool for checking PR of the site or you can simply check PR in mozilla firefox by installing Google toolbar. There you will see the green line, which gives PR of the site.