If you use Firefox, then you might be interested in the free search engine page rank checking tool that will tell you what your blog's page rank is not just for Google, but also for Yahoo! and Microsoft Live Search.
Most bloggers are interested in their page ranks for a few reasons. A high page rank signifies popularity (and an SEO strategy that is working) which can equate to more opportunities in the form of exposure, advertising revenue, and more.
What page rank checker do you use? If you've tried this Firefox page rank checker extension, leave a comment and share your experience with it.