I only knew about roughly one-tenth of them.
A notable gap in the list is the excellent Civil War Memory. It definitely belongs among the top 50, and has a lively community involved with it. I’m not a Civil War historian, but I think it’s imperative to stop by CWM now and again.
The best title on the list, I’d say, belongs to a military history blog: Mark Grimsley’s Blog Them Out of the Stone Age.
It’s a great read, as you’d expect from this author. I just learned that one of the latest crises to occupy members of our fearless Congress is the supposed demise of military history in the schools. I think Grimsley’s comment is worth your time.
Update: As of January 2012 Grimsley’s blog has been obliged to migrate because of malicious code that got onto the web server for the
warhistorian.org domain. I have updated links to point to the safe site, but because of resemblance to the content of the corrupted site, you may get a warning from your browser.