This texture pack converter works for older mc texture packs (<=1.5.x).
Look here (download broken) if you use windows.
If you need one for newer texture packs, look here or here

Depends: Linux, imagemagick (usually it's already installed)
License: WTFPL

• open a terminal and move to the folder (cd)
• run wget https://raw.githubusercontent.com/HybridDog/minetest_TPconverter/master/TPconverter.sh; sh TPconverter.sh size
• take the textures from the folder minetest

eg.
$ cd misa; sh TPconverter.sh 64

I was too lazy to add every texture, so some stuff could be missing.

CTU 1.4.x converted: