If you want to try out the Nintendo Wii Homebrew Channel, you’ll need to do the Twilight Hack. To do that, you need a Fat-16 formatted SD card. Here’s the command to format the card on Mac OS X (1.5 and 10.6):
diskutil partitionDisk /Volumes/WII 1 MBRFormat "MS-DOS FAT16" "WII" 1000M
WII is the name of the drive. The
1000M at the end is how big you want the partition to be, but if the card only has one partition, it will use the whole card, anyway.