Ok thanks to all, I am going to have to research your replies as I don't understand half of the acronyms.

Mesh networking to gain Internet access through a gateway is of interest, but what intrigues me more is the possibility of using mesh networks that are not necessarily connected to the web. Just little casual networks that are geographically dense. What sort of live, collaborative applications could that lead to?

Any ideas? Chat, video calling/conferencing, multi-person games, neighborhood watch, virtual town hall meetings ???

(Most of the applications on the OLPC allow for sharing, but without a second OLPC nearby I am not sure what this really means).