Windows: PhotoLapse is a tiny and portable application for stitching together images into a time-lapse video. Point it at a folder full of pictures, and you're mostly done.
All your time-lapse options are displayed in a single pane when you launch the 158k application. Select your directory of videos, load the images from that directory, and then tweak a few small settings like whether or not you want every image to be included or every Nth image. In the above screenshot, we've imported our test images and are about to create the movie. Spawn and Murphy the Cat Attack Mothra's Couch should be coming to an indie-friendly theatre near you, any day now.
Since our sample movie isn't theatre-ready however, we'll direct you towards a time-lapse video created by the program's author:
Have a favoured tool for creating time-lapse videos? Let's hear about it in the comments. PhotoLapse is freeware, portable and Windows only.