I don't know if this would constitute "cool stuff" but I sell television commercial time to advertising agencies here in town. Five years ago the only thing I was selling was television time.
As television stations are trying to find ways to squeeze more money out of advertising, they have begun to aggressively sell their station's web site. The numbers of eyeballs are enough to justify taking some of the client's budget. It used to be just a few tiles or banners and that was it. Now we are selling pre-rolls before streaming video of news stories and commercials inside of the streaming episodes (VOD) of Lost, Greys and Desperate. The newest platform I have been selling has been mobile. We are selling clients logos on the cell phone's streaming videos from the television station. What will they think of next. It sure keeps my job fresh.
I commented on a blog earlier wondering if they allow advertising in Second Life? If it can generate revenue for SL, it won't be long before they sell out to cell phone, computers and ISP's. Are there virtual billboards in MUD's. We see that in many of the popular video games now.