While I appreciate Ant for automating java projects build, I still often find cases where I go "jeez, it would have taken two lines in a Makefile and I can't see how to do that with Ant"

Last case I came across: I have a bunch of JPG files and I want to make GIF thumbnails from them. ImageMagick does the job pretty well, but I want to automate the operation so that only newly added or changed JPG are reprocessed at each build.