First, what do you mean with promotional videos? Try to make some videos then you promote your product through these videos? Well, most times it doesn't work well. You should create something entertaining to make a success in YouTube.
Sorry I was not clear in the first post. I am looking for a software that can create a video from still photographs which can be uploaded to youtube. Hope its clear now.
If you're on a pc, MS, they have a movie maker program as well. I don't know how good it is. I use Adobe Premier CS3 for my videos.