There is a neat little utility called disktool that allows you to mount and unmount disks (and iPods) from the Terminal. Here are some of the commands that I use...
% disktool -l
% disktool -m diskXYZReplace XYZ with the disk number of your iPod, which you can find using the "-l" option when the iPod is mounted; my iPod is "2s3", so the command I would use is "mount -m disk2s3".
% disktool -u diskXYZFollow the example above to replace XYZ with your iPod's number. It does not tell you that is ok to disconnect the iPod.
% disktool -e diskXYZHowever, this does not allow you to remount the disk. Use it after you are sure that you don't want to remount your iPod.
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