I'm still relatively new to Civ 4 - now up to third level.

From various threads/guides, I realize that you want certain buildings for special goals (banks for commerce, library for science, etc). However, in every game I've played so far - and I usually go for space race - my main cities (the one's I founded early in the game), end up having almost every building possible (except maybe for some of the more recently available buildings such as nuclear plant). Partly, I tend to take the suggestion the computer gives. But partly, it's also because I don't know what else I should be doing. If I do have one production city producing all the military units, then buildings seems to be the only other option for a city. Or should I have the cities switch to the "Research", "Weath" or "Culture" option?

Thanks for any insight.

Unless you are gunning for a cultural vic or need an extra kick to finish that last tech before starting Apollo Program, don't build culture, resource, or wealth. Hhaving a city build wealth adds up to almost nothing by the endgame and actually subtracts from your power by sucking out a possible production center. If you are a space race person, definitely build libraries, universities, etc. However, by endgame, you should be building a very modern army. On the later levels, you will get invaded if you are ahead in the space race, so you want to avoid any bad habits. Get Scotland Yard and deploy spies into all of your major production cities, any cram units into them as well to avoid enemy spies sabotaging your space parts. And if you are really getting low on stuff to build, then spam marines and launch a massive amphibious assault on random coastal cities w/ transports and battleships. Hope this helps
-jcw

You should look into the various threads on city specialization on this board. It will help you focus your build queues. Also, if you can build everything available in every city, it sounds like you're ready to raise your difficulty level from Warlord to Noble.