I'm not really sure what to search for to find this, but basically I'd like to allow people to upload their banner to my system and then when people click their link to my site their banner is then displayed...it then changes when another website which has signed up sends someone over and it then displays their banner.

A bit like the last 10 refers on this website:

http://radiotoolbox.com/


Any ideas? thanks :)

Well, you'd need a database to store their info, then a script to look just change to the appropriate banner when a visitor arrives with a matching referrer string.