Woofer, Twitter, Squeaker
Courtesy of links from a discussion thread on Otavia's recent Facebook post:
Woofer: Just like Twitter, except that any given post must be at least 1400 characters long. (That's roughly 230 words, or about a page of typewritten double-spaced manuscript; about two-thirds of a page of a paperback book.)
Squeaker: Just like Twitter, except that any given post must be exactly 14 characters long; no more, no less.