This is a video of a K'nex ball and roller-coaster machine Adam and I made a few years back. The starting image was created with Blender using 3D models Adam made with me. There are a few artifacts in it, but overall I'm pretty happy with it. And the video's no longer on the FTP site.
We also made a ball machine that we entered into the 15th Anniversary K'nexpert search (2007). We made it to the semifinals, so a picture of our creation was posted on the K'nex website, but we didn't make it to the finals. The finalists for that year (split into age groups and categories, with two in each division) were chosen by online voters, so I'm inclined to think that we were ripped off. Our competitor had made a turtle. I do not understand how a turtle like that, though fine in and of itself, could possibly be perceived as better than our amazing, room-spanning machine. I'm not sure how we would have handled the prize money, though, since it was going to be held in a trust or something like that and there were two of us instead of one. In light of that, perhaps our loss was for the best.
In any case, here's two pictures of it (click on them to see them in full resolution):
And here's some other things I've made. Mainly, a ferris wheel and a trebuchet.