Ubuntu's JeOS (say 'juice' if you must) weighs in at 151 MB. Want to roll your own VMware miniappliance? JeOS is a pretty good place to start.

The Ubuntu Server Edition JeOS 7.10 is custom-tailored for independent software shops or anyone else with an itch to build a tiny, tiny virtual appliance. Again, the ISO is only 151 MB. (It took me less than a minute to pull down the current 99 MB 8.04 beta.)

This isn't your open source pal's warm and fuzzy Ubuntu Desktop incorporating all the pretty bells and whistles. This is a lean, no-GUI, get-your-server-running-in-a-VM build. No extraneous drivers are invited to the party ... which means no SCSI drivers, so make sure you have an IDE drive on hand and available to VMware when you first fire JeOS up.

Rusty at the Linux command line? Soren Hansen and Nick Barcet moved their step-by-step tutorial to Linux Magazine earlier this year. Loyal, lively readers of that site have posted jeers, corrections, and suggestions, including strategies to shrink resulting vmdks. The community being what it is, the tutorial and all mods will eventually be posted at the Ubuntu Wiki.

A tiny-footprint server OS with minimum hardware reqs. What a novel ideal.