Here is how you mount your Macintosh HFS partition.  The same 
process will work for any Macintosh HFS formatted drive 
(Zip, Jazz, whatever), but NOT with any HFS+ formatted drive.
With luck HFS+ support will be available Real Soon Now.
(When it becomes available, I'd appreciate it if some enterprising
individual would update this note with the appropriate 
instructions to make it work.)

You should do the following as root:

1. Find out the device number for the HFS drive in question
(ie. /dev/sda5).  An easy way to list the available partitions
is to use the command "pdisk -l".

2. Make a mount point.  This is where you will "cd" to to
access your HFS drive.  For example: "mkdir /mac"

3. Add a line to the file /etc/fstab that looks like:
/dev/sda5        /mac          hfs    defaults,umask=0,quiet 0 0

   ^^^^          ^^^^          ^^^          ^^^^^
partition id     mount point   fs type   mount options

This tells the system to mount the partion read-write and
sets the file permissions to rwx for everybody.  If you
are concerned with file-system damage, replace "defaults" with
"ro" to force read-only access.  For a removeable, use
"user,noauto" instead so any user can use the command
"mount /mac" whenever a disk is available.  (Use
"umount /mac" before you try to eject it.)

5. You can mount the partion immediately with the command
"mount /mac".  The filesystem will automatically be properly
mounted and unmounted on subsequent reboots.

If you nuke your drive, restore from your BACKUP and 
add to this note if applicable.