CrisisCamp is using both Wikis and Google Wave for their effort in collaborating with their support. CrisisCamp is about helping NGOs with supporting their technology needs.
Their main wave can be found on this link. The Goal with the Wave is:
Join camps, activities, people and learning in this effort to support Haiti. And do this synchronously and in real time.
It seems that Google Wave will provide a better helping. But it is fair more accessable than a wiki, and you can start with editing with out the hassle of wikis.
I sure hope their efforts will help save lives in Haiti.