(Only just noticed this thread) Hmm I've had similar problems actually, I had a prop_static object (a big kind of kart) and it never showed up, though I added a car in which worked but looked kind of stupid because it had no windows.
Try searching on Valve's dev wiki
http://developer.valvesoftware.com/wiki/Main_Page
Other good sites:
http://www.iwannamap.com/
If your mapping counter strike:
http://www.fpsbanana.com/tutcats/6