You could build a video conversion website where one uploads original high resolution video and it'd spit out 1080p/720p/320p and other formats of video that are suitable for delivering on different devices/bandwidth. This could be an alternative for people hosting video on youtube and getting slapped with ads. An effort like this would use a lot of CPU but once it's converted it's just the storage cost. Common challenges are copyright issue but I can see different ways to promote it as a professional service than collection of random videos. $100K would cover cost of offering it for free to people for a limited period.
As strange as it sounds, that much bandwidth would probably suck up $100k faster than you'd imagine. There's a reason a lot of large companies that deal in video have their own data centres and crazy bandwidth deals that make it cheap. I don't think $100k at Amazon's prices would last more than a few months if the service became popular.
