My kids want to try their hand at creating animated Lego films like those that can be found on YouTube (after making one at the Lego exhibition at Thinktank in Brum), anyone know of a free software for this. Alternatively, how can you stitch a series of stills together as a movie clip?

There’s this: http://www.irfanview.com/

You can make a slideshow and get it to display each slide for a very short amount of time, effectively stitching stills together to make a clip. Not sure about adding audio.

There’s probably better out there, but I’ve used irfanview to make some cool timelapse films.