Melmac is the trade name for melamine, a substance that Webster 1913 apparently knew about, but was turned into an incredibly tough, hard plastic by the American Cyanamid Corporation in the 1940s. There appears to be precious little information about the history of Melmac on the Internet, which is surprising: in the recent "retro" movement, Melmac dishware has become a hot item for collectors. A search for Melmac on eBay turns up many hundreds of items for sale, some of them selling for well over $50.
Anyone who remembers the 50s and 60s should have fond (or horrific) memories of Melmac in the kitchen. The younger among us who grew up in older houses might have the same memories; I grew up with a set of pea soup green Melmac bowls that are still in use today. As a material for kitchenware, Melmac was popular for two reasons: first, that it was incredibly durable, unlike china or ceramic; and second, that it could be manufactured in a wide variety of interesting colors and shapes. For households with children, dishes made of Melmac and other plastics were invaluable; how many times could you replace a ceramic dish that the baby knocked off the table before breaking the bank? Melmac is tough -- touted as being unbreakable (in an art seminar I took many years ago, the teacher demonstrated Melmac's strength by bashing a Melmac bowl against a desk; unfortunately, the bowl broke) -- and lightweight. This, combined with the designs in which Melmac dishes were made, meant that the same dishes used for everyday dinners at the dinner table could be brought outside for a barbecue or picnic. Toward the end of Melmac kitchenware's popularity, more "elegant" designs were even made, with decal patterns resembling traditional china dishes. Many of the early designs for Melmac dinnerware, too, were innovative and interesting in their own right, whose elegance was enhanced by a non-traditional look -- the house of tomorrow, today!
So why don't we see more Melmac today? First, it's tacky. Imagine going to a dinner party and being served on lightweight plastic dishes -- even if they are retro-cool. It's just not done. More importantly, though, despite Melmac's strength, it's incredibly easy to damage. While your Melmac dishes will be around for many years, they will quickly start to look used and abused. It's very easy to scratch them with metal utensils, and they have a habit of retaining the stains from dark-colored liquids. Your Melmac tumblers probably won't break after being dropped a few hundred times, but the sea-foam green will start to take on a little of the orange from your morning juice; your bowls will withstand the dishwasher a thousand times over, but eating out of them with a fork will leave them scratched and dirty-looking. Many people saw this staining as being unsanitary, although really, the dishes are still perfectly good after all these years. Finally, you certainly shouldn't leave Melmac dishes anywhere near your stovetop: it will scorch a hideous brown-black that will be impossible to remove.
It may not be an elegant choice for dinnerware today, but if you're outfitting a retro-themed kitchen, you can't be without a few pieces of brightly-colored Melmac. You can find it at many antique shops and on eBay, but your best bet for low-priced Melmac dinnerware might be yard sales at older households. They're bound to have a few pieces, and would probably be glad to sell them to you at a fair price. Plus, you'll get to talk to interesting older people, which is usually a pleasant and rewarding experience.
References:
Flora Hartford's Humanities 10 Art Seminar, 1994-5.
http://www.theoldtimes.com/past/899_1.html
(Yes, ALF was from the planet Melmac.)