Many of the leading game designers have blogs that I've found entertaining, so here are a few of them.
- Ken Hite's Journal: Ken Hite, master of occultism, conspiracy theory, and bisociative thinking.
- Dork Tidings: John Kovalic, who while not a game designer as such, has done tons of gaming artwork.
- Oops, Wrong Planet!: Doc Cross, creator of Toon among other things.
- Robin D. Laws: Designer of a whole mess 'o nifty, including Over the Edge, Feng Shui, and the Dying Earth RPG.