Inventory Control Across Multiple Servers .. Ideas?
I'm not sure if there is any one really good solution for your problem.  I think the way you are doing it now works fine, but if you don't agree then I don't know what to tell you.
We currently have an inventory management system that was built in-house. It works great, and we are constantly innovating it. 
This past Fall, we began selling products directly on one of our websites via a Shopping Cart checkout.
Our inventory management system runs off a server in the office, while the three websites we currently have (only one actually sells things) runs off an outside source, obviously.
See my problem here? Basically, I am trying to think of ways I can create a central inventory control system that allows both the internal software and external websites to communicate so that inventory is always up to date and we are not selling something we don't have.
Our internal inventory tracking works great and flows well, but I have no idea on how I would implement a solid tracking system that can communicate between the two.
The software is all written in Python, but it does not matter as I am mostly looking for ideas and methods on how would this be implemented.
Thanks in advance for any answers, and I hope that made sense .. I can elaborate.