Mounting a partition with defaults parameter will give all users read/write access. As quoted from Swerdna's openSUSE mounting tutorial:

To mount your NTFS partition
permanently, add your version of the
following line into the file system
table, fstab. [and leave the last line
in the file as a blank line.]
Recommended option for world-writeable
mount:

/dev/sdb1    /path_to/mount_point    ntfs-3g    defaults    0 0

When you reboot, the partion will
mount into the folder
/path_to/mount_point with permissions
drwxrwxrwx, i.e with read/write access
for everybody, in the style of
Microsoft's insecure filesystems.