SlowmoVideo is a slow motion video editor that allows for slowing down footage by large factors, calculating intermediate frames using optical flow. Initially only available for Linux, there's now also a Windows version available.
Some of you probably remember that little program Slowmo video that was posted here on BlenderNation a while ago. Well, for those of you windows users like myself who wished you could try it out but couldn't, your hour of glory has come! As of August 13, 2012 there is a windows binary available on the site for you to try out!