Geo-targeted advertising is a concept used by many leading advertisement serving providers. The concept revolves around providing location aware advertisements to the user. That means, if your website visitor is from USA, the system should pick up advertisements targeted at US visitors. If your visitor is from Malaysia, then the system should deliver advertisement specifically targeted for Malaysian users.

The overall setup would be like this -

1. The central server accepts advertisements in the form of image banners of specific size.
2. The advertiser specifies the location which he intends to target.
3. Advertiser also specifies how long he wants the advertisement to be displayed, how many visitors and other factors.
4. The system provides a login to publisher as well.
5. Once the publisher creates account, he/she is presented with a small snippet of code which can be embedded in any site.
6. The code snippet will determine the website's visitor's location using IP address or other mechanisms and deliver the relevant advertisement.

The whole model can be deployed in a small network of computers. 😀 If you need help in developing this idea further, ask your specific questions in this thread. 😀