This is addressed on the FAQ
here. Starting with whichever version that you have and using a media converter like QuickTime Player Pro ($) or MPEG StreamClip (free), simply open the file and then export to the format that you want.
We are no longer providing an iPod version since it is now relatively easy to make and the various sizes and formats keep expanding.
The 'Best Way' is always to start with the highest resolution (HD) and then down-rez/cross-rez to the appropriate format required.