Any good mods that let you run a business? Or run anything like a guild or a city, etc...

Let's see theres the http://www.gamesas.com/?showtopic=931523&hl

Kvatch rebuilt, and other "Kvatch ____" mods which usually end with you owning the city

Integration has you start 1 guild, help 4 other guilds, gain money from an art gallery you help setup, and you establish a city which you're figurehead of.

Gweden Brothel has you recruiting prosttutes and turning the Siren's Deception place into a actual business

can't think of much else off the top of my head

Order of the Nibenay lets you start your own guild, I think. Anyways, I think you'd get better results in the mod detectives thread.

Look for one called "Big Business" - it lets you run a farm. Specifically

What I'd love to see done though is one that lets you run a full blown shop that reasonably simulates NPCs buying and selling things at it.

There's also Pat's Business Mod. Which does what Arthmoor wanted.