Several online services to convert djvu files to pdf (and other file format conversions):
Design, Illustration, Typography, Code, Mac, Unix / Linux, Lifestyle & whatnot.
A nice tutorial to convert a bunch of images into a movie sequence with ffmpeg and mmencoder. Includes a script to get the job done.
Another experimental tutorial (ffmpeg + mencoder).
Videolan (VLC) website.
15-useful-batch-image-processors (smashing magazine)
Using the terminal in Linux, Imagemagick is very powerful, with its mogrify command.
In Windows, many of the image processing programs listed at Portable freeware can operate in batch mode.
Images can also be processed by Python and Perl (with the respective help of PythonMagic and PerlMagick, an interface to the popular ImageMagick suite of command line tools to do just this kind of stuff. Or its fork, Graphicsmagick ), of course PHP, Ruby…
Python’s PIL (image library) comes also handy for the task.