Windows/Linux: Free, open-source application PhotoFilmStrip creates video from photographs quickly and easily, complete with effects, a soundtrack and smooth zoom in/out effects (commonly referred to as the Ken Burns effect).
The cheesy cat video above demonstrates PhotoFilmStrip in action. Creating your video from still images with the app is a breeze. Just drag and drop pictures you want to use into the application, select the effects you want to use (if any), determine the settings for the pan and zoom Ken Burns effect, and, when you're done, add some background music and export the video to DVD, XviD, or one of the other supported formats. (It can even export in HD.)
PhotoFilmStrip is a free, open-source application for Windows and Linux only. (Mac users, iMovie actually comes with its own Ken Burns effect for still images.) As FreewareGenius points out, it doesn't have a lot of bells and whistles, but it handles what it does really well. If you give it a go, let's hear how you like it in the comments.