Beyond the Black Gate is one of the blogs that I truly look forward to reading. The author has now compiled an index of all of his rather extensive and very informative articles on Megadungeons to make this high-quality stuff more accessible. Here's hoping that he does a PDF compilation of all of this ultra-good stuff!
Mandragora is another blog that I've only just discovered from a recommendation at another blog, it's by an old-school veteran returned to the scene and it's well worth a visit.
I'm also a big fan of Warlord Wednesdays over at The Sorcerer's Skull. If you remember Mike Grell's sword & sorcery comic-epic, check it out.
Last, but not least by any means, is Vaults of Nagoh, a fellow-traveler in weirdness and post-singularity outre ideologies certain to make the average iconoclast quake in their boots.
And yes, Planet Algol & Bite the Bulette are right at the top of my list of personal favorites. I just wanted to plug a few others this time around.