My favorite Gazetteer is definitely the Principalities of Glantri written by Bruce Heard. It is probably the gaming product I have used the most throughout the years, so you can probably imagine how cool it is for me to see that the man himself, Bruce Heard, has a blog.
Without further ado I present the link.
Update: He’s on Twitter as well https://twitter.com/#!/Ambreville
Coolest handle ever!