If the Disk Utility GUI on OSX doesn’t allow you to format a USB Stick or SD Card with FAT32 the command-line does.

1. List the available disks with: “diskutil list”
2. Find the device you want to format eg.: “/dev/disk2” and use this device in the next command.
3. Format with: “sudo diskutil eraseDisk FAT32 DISKNAME MBRFormat /dev/disk2″