This PC 'drag and drop' tool allows you to batch convert 24bit bmps to 16 bit bmps quickly and easily (as compared to gimp, for instance). It's targeted for DS skin making and animated frames for the R4 Wood firmware.
Video: http://www.youtube.com/watch?v=Ai3tUf6vj9Q&feature=player_embedded
Video: http://www.youtube.com/watch?v=Ai3tUf6vj9Q&feature=player_embedded