Daily Kos and TPM are so different that "blog" is much to thin a word to describe them. KOS publishes diary's submitted from anyone. They are ranked by the community. Markos is the owner but not by any means the most prolific or even most important poster.
Josh on the other hand is a muckracking reporter of the old Jack Anderson mold who can interact with his readers in ways never before seen. The release of 4,000 pages of info in the first document dump in the AG firing scandal and the rallying of Josh's readers to examine those pages was a good example.
And if you haven't alrady been following it, [link|http://www.firedoglake.com/|Firedoglake] is well worth a gander. No question, the Libby/Plame/Rove/Novak debacle was best covered by FDL. Their trial coverage was a tour de force that was the envy of other reporters.
KOS, TPM and FDL are absolutely different in fundamental ways yet all are called blogs. Similarto the way Good Morning America and 60 Minutes are both called news.