Google has an online word processor called Google Docs. One feature of this program is that users can share documents and have multiple people viewing and editing the same document at the same time.
Thinking of this feature has given me the idea of finding another Game Master willing to help me with an idea. My idea is that myself and another GM could co-write an adventure (using a system that we agree upon) and then we would both run that adventure with our respective groups. Afterward, we could get back to each other with the stories of how things went and how each group played the adventure.
This would give the GMs another mind to conspire and get ideas from, as well as an interesting account of the same adventure put to different minds.