Like there's not enough to do around here...
The concept is simple. I start a comic by making one panel and posting it. Someone else comes along, adds their own panel, and reposts the strip. A third person comes along and finishes the strip.
The next person will then start a new comic with one panel somehow related to the first comic. In this way, we create a series--one panel at a time.
Rules:
1) You can't add two panels in a row. Also, you should keep a two-panel cushion between your own panels.
2) If two people happen to post panels at the same time, then both series may be added to by subsequent users (while still observing Rule 1).
3) If you want to add a numbering system to the comic title to keep up with the iterations, that's fine. Just keep it simple.