as a starting point, try this in your /etc/fstab:
/dev/sda1 /mnt/sda1 vfat users,defaults,umask=002 0 0
This would be for fat32 and would give the permissions -rwxrwxr-x to the files on the drive. Also, try doing 'chown <username>.users /mnt/sda1' prior to mounting the drive. This is the proper way to change ownership of the folder.