If you are doing something to a bunch of files, perhaps a shell script like:

for i in *jpg; do something $i somethingelse; done

and want a simple way to parallelize this, try xargs, which I love:

ls *jpg | xargs -n1 -P5 -I% something % somethingelse

will run on five files at a time. I've used this trick two or three times today in re-synchronizing photos from two phones and a camera and an SD card and Dropbox. #xargs #shell #protip