The command for giving everyone read-write-execute access (as you tried with the chmod) would be
Code:
mount -o umask=000 /dev/sdc1 /usb
A better way for doing this is adding the line
Code:
/dev/sdc1 /usb vfat noauto,user 0 0
to
/etc/fstab. You can then simply
mount /usb as a normal user (and you'll own everything in /usb).