You can use the livecd/liveusb/fromiso live (as well as installed antiX) to install an antiX.iso file to usb stick via the antix2usb application.
1. Boot from live media
2. Open antiXcc -> Disks -> antix2usb, provide root password
3. Select Iso file - Navigate to the antiX.iso file
4. Choose a system partition size of circa 10 MB bigger than the selected Iso file
5. Set options for antix2usb ie persistent.
6. Make sure hal is disabled before hitting Apply (/etc/init.d/hal stop)
7. Once finished, you should have a bootable live usb stick with persistence enabled
8. If you have an older computer, you might need to add this to the /boot/grub/menu.lst to stop being dropped to a limited shell, when booting from the usb stick.