I didn't actually read this book, but I did compile the 27 blogs that New York Times journalist Sarah Boxer lists in her book as masterpieces:
Angryblackbitch
http://angryblackbitch.blogspot.com/
Becker-Posner Blog
http://www.becker-posner-blog.com/
Click Opera
http://imomus.livejournal.com/
Cosmic Variance
http://cosmicvariance.com/
Diary of Samuel Pepys
http://www.pepysdiary.com/
El Guapo in DC
http://elguapodc.blogspot.com/
Eurotrash
http://www.upsaid.com/eurotrash/
Get Your War On
http://www.mnftiu.cc/mnftiu.cc/war.html
Go Fug Yourself
http://gofugyourself.typepad.com/
How to Learn Swedish in 1000 Difficult Lessons
http://francisstrand.blogspot.com/
I Blame the Patriarchy
http://blog.iblamethepatriarchy.com/
In the Middle
http://raedinthemiddle.blogspot.com/
Ironic Sans
http://www.ironicsans.com/
It's Raining Noodles!
http://raining-noodles.blogspot.com/
Johnny I Hardly Knew You
http://jihky.blogspot.com/
Julia {Here Be Hippogriffs}
http://julia.typepad.com/
Language Log
http://itre.cis.upenn.edu/~myl/languagelog/
Matthew Yglesias
http://matthewyglesias.theatlantic.com/
Micrographica
http://www.serializer.net/comics/micrographica.php
Midnight in Iraq
http://midnight.hushedcasket.com/
Ninapaley.com
http://blog.ninapaley.com/
Old Hag
http://www.theoldhag.com/
Radio.Uruguay
http://dgoutnik.net/
Rootless Cosmopolitan
http://tonykaron.com/
The Rest is Noise
http://www.therestisnoise.com/
The Smoking Gun
http://www.thesmokinggun.com/
Under Odysseus
http://www.underodysseus.blogspot.com/