ZunaVision is a video technology that movie studios have had for years, brought to the average user by the computer science department at Stanford University. It lets you place images and videos within existing videos. Want to put a poster or an advertisement on a building in the background of your footage? ZunaVision's got you covered. How about changing the painting in a picture frame? It can do that, too.

ZunaVision isn't very hard to use. You can just select a surface, and it does a capable job of making your image look like it could plausibly be hanging there. It's not just pasted haphazardly on top of your video. It's cool enough that I'm already worried it won't stay free for long. The last Stanford web toy I fell in love with, Vector Magic, turned into a pay service after a while. Zunavision looks like it could be worth selling, too, but maybe the creators can just turn a profit by sneaking ads into other videos.

UPDATED: The URL for Zunavision changed, so the links in this post were broken. They should be working now. Thanks to all the readers who pointed that out!