Here is another Google Wave video by Joe Sabia. He previously introduced the world to Google Wave by doing a Pulp Fiction re-enactment. This one is more comprehensive, and still answers zero questions on exactly how to use it.
At this point, it's hard to see what else Google Wave is used for besides making cute internet videos. Why would anyone have a need to do any of this stuff? it all seems so superfluous. Cool, but superfluous.