Eric Sammons, whose book Who Is Jesus Christ I highly recommend, has updated his popular listing of the most popular Catholic blogs.
It is based on how many Google reader subscriptions there are for each blog and, as such, is just one way to measure popularity. Still, it is as valid a way as any others that occur to me ... and the list is interesting and seems more accurate (for one thing The Curt Jester is now included).
You can see the top 25 blogs here and there's a link at the bottom that has the top 200. It is fair to say that you'll find some good and diverse reading among the blogs in the lists.
(I was interested and actually fairly surprised to see that Happy Catholic managed to scrape into the top 25 ... which tells you the wide range of subscription numbers which goes from almost 7,000 down to 750. It doesn't really mean anything in particular but is just interesting to see the breaks in numbers.)