If you have noticed the shared side bar is missing when using Leopard there is an easy fix for this. From the command line:

$ sudo pico /etc/smb.conf

Now add the following line to the [global] section:

name resolve order = lmhosts bcast wins

Save it the file.

Disable and re-enable file-sharing from the Network panel, checking "Advanced" to make sure that SMB is enabled.

Wait a few minutes and then you should see the sharing side bar.