Classic science fiction/horror film, released in 1958. It was directed by Irvin S. Yeaworth, Jr. and written by Kay Linaker and Theodore Simonson. It starred Steve McQueen (in his first major role), Aneta Corsaut, Earl Rowe, and Olin Howlin, among others. It featured a really goofy theme song called "Beware of the Blob", written by Burt Bacharach and Mack David.

After a meteorite crashes to earth, a protoplasmic alien life form emerges and begins to absorb humans, growing larger as it consumes more people. Eventually, it is the town's teenagers who defeat the monster when they freeze it solid using fire extinguishers.

I believe that part of the reason this movie was such a sensation was that people in the 1950s were obsessed with cleanliness, and the idea of a filth monster was really scary -- and certainly, one of the best high-concept horrors ever created. It was followed by a poorly-received 1972 sequel called "Beware! The Blob" and not-entirely-successful remake in 1988.

Lieutenant Dave: "At least we've got it stopped."
Steve: "Yeah, as long as the Arctic stays cold."