Have you read the "Races of the Dragon" suppliment for recent AD&D?
Kobolds take up a full chapter, and that chapter's probably the best one in the book. The descriptions of their society (Socialist, with an emphasis on work ethic), their culture, their religion, all that is really amazing.
Modern Kobold backstory is that they were created when the first dragons were born onto the earth -- when the blood struck the ground, they sprung fully formed. While that may or may not have happened, a major factor with the Kobolds is that, dispite every hardship they ever encounter, nothing phases them since they know one inevitable truth -- they're decended from Dragons.
Surprisingly enough, as far as races go they're almost exactly like Dwarves. Very hard workers (to the point that, in full swing, a Kobold mine could out-produce a Dwarven mine), very religious (once a day, the entire Kobold den goes silent to meditate on their dragon ancestry), and surprisingly adept.
Trapmaking is their only real artform, although they have Bards and Sorcerers as well -- they usually spend their time in the mines assisting with the workers.
A major factor that no one gets is that Kobolds intentionally let themselves become underestimated. It's something they work at. It's a survival mechanism -- they know they can't compete, so they just try to get people to leave them alone and do their own thing. Works surprisingly well.
If I were to make a "Kobold Fortress" it would be similar to DF, except... take the number of PCs and times them by 10, and cut their productivity by 8 to make up for it. You wouldn't have 1 miner digging out a tunnel, you'd have 10, for example.