Atrios, Kos, & Josh Marshall ("Talking Points Memo") -- my personal mainstays -- have already been posted, so here's some other excellent sites:
http://dneiwert.blogspot.com/ ("Orcinus")
http://www.washingtonmonthly.com/ (Kevin Drum)
http://www.counterspin.blogspot.com/ (Hesiod)
http://digbysblog.blogspot.com/ ("Hullabaloo")
http://yglesias.typepad.com/matthew/ (Matthew Yglesias)
http://www.pandagon.net/http://www.prospect.org/weblog/http://www.j-bradford-delong.net/movable_type/Index.html (specializes in economic analyses)
BEST on Iraq:
http://www.juancole.com/ ("Informed Comment")
http://www.empirenotes.org/ (Rahul Mahajan)
http://scoop.agonist.org/ (lots of news from all over)
And my brand new favorite -- wacky and intelligent:
http://www.michaelberube.com/ (In order to make sense of his latest entry, you need to read back a few days. For a real treat, read back to his posts from the RNC. :D )
My old favorite:
http://billmon.org/ (the Whiskey Bar") has, sadly, been on a long hiatus. For some outstandingly intelligent commentary, read through his archives. And be sure to check out his absolutely fantastic list of links -- scroll down along the right side of the page.
These will keep you busy!
sw