Working in a tech shop, and being an Apple fan, I deal with ALL the Apple-related products. I'm seeing products from 10.4 to 10.7, and I have made a bootable flash drive from 10.6 (since it's the most popular). I have the disks (and a disk image for 10.7) for each of these that we will use if the OS ever needs reloading. Is it possible to put a disk image of all these disks onto a flash drive so when we boot with the single flash drive, it asks which OS X version to install?
I have an external hard drive with several installers on it. All you need to do is make several partitions, each large enough for the disc you're imaging. (My drive has 10.4 Tiger PPC, 10.5 Leopard PPC, 10.5 Leopard Intel, and 1.6 Snow Leopard on it, and I have a Lion USB flash drive.)
I made the images using Disk Utility's Restore feature. Select the source disc (in the optical drive), choose the "Restore" tab, and make sure the selected disc is in the "Source:" field. Drag the intended destination partition to the "Destination:" field, hit the "Restore" button, and wait.
There are several caveats to keep in mind:
One good thing about having the installers on a drive is that hard drives are much faster than optical discs.