I use bash, perl, awk and sometimes plain old 'sh'.
for f in *.flv
do
... something with "$f" ...
done
A lot of it depends on what you're trying to automate, you could use variations of the above to create thumbnails, do image conversions, produce a list of images that are different sizes, watermarks, etc..
If you can, pick software that has a command line interface (even if it's not the primary interface) because that is the easiest to automate. If it doesn't have a command line interface,
sometimes you can build one on top of it.
Once thats done, it becomes a pretty simple matter (especially if the commands are textual) to stack them together into specific tasks. I do this so often I don't even really think of it as "automation". (works best when things are uniform & organized well... "corner cases" are the natural enemy of automation)
Flip side of automation is, sometimes you spend more effort automating something than if you'd done it manually in the first place, it's kind of challenging to decide when to automation will pay off.
If you're stuck on a windows machine, install the cygwin to get access to these kinds of tools, the pathnames are all messed up, it's sluggish & annoying, but cygwin is still a lot better than nothing at all.
