- Ars Ludi seems mostly dead, but it has some awesome articles in the archive - mainly the West Marches stuff, but also in the GM craft and Game design categories. Worth a look, though maybe there's no need to have it sitting on your RSS reader feed.
- ASCII Dreams is a really nice roguelike development blog. The author is making an Angband variant, but posts are pretty rarely about that, so it's good even if you don't care for Angband (which I don't).
- Asmor is the guy who makes those great utilities for D&D 4 you might have heard of - the Monster Maker and Random Treasure Generator seem to be the most popular ones.
- Eleven Foot Pole isn't a giant from Warsaw, but a blog MST3K:ing every single room of the Keep on the Shadowfell adventure by WOTC. He's about to finish that up and move on to Thunderspire Labyrinth. KOTS gets some pretty scathing critique, but he finds a few good points with it too.
- Grognardia is what it sounds like - a blog about the older editions of D&D, circa OD&D and thereabout. Still manages to pull in a newbie like me, somehow. Must be good or something.
- Keep on the Gaming Lands is Mike Mearls' blog. Almost feels like fandom linking to it, but he usually writes good stuff, and isn't afraid of pointing out stuff he feels could be improved in that game he helped writing.
- Monsters and Manuals is just written by this guy, you know. And this stuff is just weird.
- Musings Of The Chatty DM is a good general read. Hard to point out something specific, though.
- Finally, RGRD is a Google Group (and a proper mailing list) for roguelike development. Worth checking occasionally, when it's not being swarmed with ad spam.
Well, that's my list. Hope someone found something new.