AbdulAlhazred mentioned the "Kobold Hall" mini-adventure that's in the back of the DMG.
If you run that, make the first room have a trap: the two squares in front of the pool should collapse as soon as a character steps on one of them, tossing the character into the pool. The pool should cause ongoing poison damage (save ends--when the character gets put of the pool). The kobolds reveal themselves, and start slinging gluepots/stinkpots/whatever.
Change the end dragon from white to green (hence, the poisonous pool. In fact, make poison a theme--the kobolds use poisoned weapons, some of them seem sickly and weak, the air smells bad, etc.).
Put in some hostages in the last room (before the dragon's lair) that the characters want to protect (children, relatives, important persons, etc.), but who get in the way.
Add more treasure; it is a dragon's lair, after all, and this dragon has been having the kobolds attack travelers and merchant caravans for some time, plus, it has plundered the hall, so the loot should be good.