THIS IS AWESOME - PageRank Checker

http://www.prchecker.info/check_page_rank.php

CHECK THIS OUT!!! You can check the PageRank of any website!!! It turns out, the PageRank of pandora.com is 8 out of 10 possible points! This website also has a feature that lets you add the PageRank checker to your own website, which proves the importance of PageRank. Websites can use this function to display openly the PageRank value of a website, which indicates the quality of the information on that website. If the PageRank value is high, that means many pages link to it, which means that the information is most likely credible and accurate.

Pre-Firefox, I used to use Google Toolbar for Internet Explorer. The only feature I miss from the toolbar was an integrated "PageRank meter" which let you see exactly the PageRank of any given site you were visiting. I found this to be much more useful in leading me to reliable sites than any other similar thing (stumbleupon, delicio.us, etc), presumably because PageRank aggregates these sites among others.

It turns out google toolbar still exists: http://toolbar.google.com/ - and now it's for Firefox too!