I have found that having an installer DVD with me at all times can be very useful. I don't like to actually carry the DVD with me, so I made a 10GB partition on my boot disk (MacBook Pro). I restored the Leopard DVD to this partition. Now all I have to do to boot from the 'Install DVD' is to use the Option key when I boot.

That's not the tip, however; this is. I may want to launch an application other than the ones found in the Utilities menu. Since Terminal is there, I tried to use Terminal to launch (using the open command) other applications. open, however, is not on the Install DVD, but it will still work if used from another partition. For example (assuming system is my regular boot volume):

/Volumes/system/usr/bin/open /Applications/TextEdit.app

But what if the regular boot partition is shot? The answer is to copy the open command from the regular boot partition to the installer partition:

cp /usr/bin/open /Volumes/installer/usr/bin/.

Now I can use the open command from Terminal when booted from the installer partition. When DiskWarrior comes out, and the other commercial disk repair tools, I will copy them into /Volumes/installer/Applications, and be able to launch them when booted from the installer partition. Note that this may work in Tiger, but I haven't tried.