Zip drives, expecially the 250 meg models, are a MUST for OS repair as I see it. On a 250 meg disk I can fit Windows 98 SE, Partition Magic, Cygwin, and Ghost, or a Linux kernel, every module I could possibly want, bash, vim, cfdisk, XFree86, and Blackbox!
Before you even say the word "CD-RW" in reply to this, let me point out that although you might be able to boot Linux into a ramdisk, your configuration when you burn is perminant and inflexible, and Windows won't boot at all! Zip disks are readable and writable, so Windows can boot and Linux can be altered.
Until another removable storage medium, which can be used with any OS, on many different architectures, and can be read and written like a floppy, is created, Zip will live on.
As for Jaz, it was never popular simply because it was too expensive.