We wrote about Flexi-Discs a while ago - records inexpensively produced on flexible vinyl - cheap enough to be part of direct mail campaigns, giveaways, and the like. Another sort of "ephemeral" record was produced simply by laminating thin plastic onto cardboard.
Cardboard records were light and cheap enough to be mailed or included in magazines, but I remember them best from the back of cereal boxes. From my childhood, I've got a square record that told the spooky story of Sleepy Hollow. The Jackson Five record above was also cut from a cereal box (by someone who hadn't mastered scissors apparently); a sampler of what you could expect from the Five's latest full LP. Grocery store shelves weren't a friendly environment for a naked record, so lots of the ones that I've got sound pretty bad - if they even work at all (over time the plastic layer can peel away from the cardboard backing).
Today DVD's and CD's are cheap enough to include in countless promotional campaigns, and are sturdy enough to last almost indefinitely. Cardboard records are much more vulnerable to the ravages of time than conventional discs. They were designed only to be played a few times and then forgotten, since they often cashed in on some fad or were part of a current sales pitch. Due to their obscurity, and the low value placed on them by collectors, it's unfortunate to think that many of these unique recordings are probably lost forever.