Here are a few more that you might like.
http://www.matthewyglesias.com/
Center left political/philosophy blog, written by a recent harvard grad.
http://www.prospect.org/weblog/
The American Prospect's weblog. Matt Yglesias is a writer there, among others. Good quality stuff.
http://www.crookedtimber.org/
A scholarly, progressive group blog. It's a newcomer on the scene, but has quickly developed a strong following due to its strong content.
And, a couple of good conservative blogs that you must read in order to have a balanced view of the world. If you only ingest stuff you agree with, you never get any kind of bullshit check, cause you know there's just as much liberal bullshit as there is conservative bullshit.
http://www.instapundit.com/
Instapundit. Glenn Reynolds. The godfather of conservative blogs. He's more of a libertarian republican than a texas/southern republican, which is actually typical of republican bloggers. He updates at an insane pace.
and finally,
http://volokh.com/
The volokh conspiracy, a conservative group blog run mostly by lawyers and academics. Very content rich. Frequently updated.
That's all I got. You can find out about other sites from the ones listed here. I'm a fan of blogs as a source of political arugments and news. You still have to hit up WaPo and the Times, but blogs are good about commenting on a story from a certain point of view, but also giving you the link so you can read it for yourself.