On September 19, 1982, (bearing in mind the international dateline, that's today for us in Australia), Scott Fahlman posted to a bulletin board at Carnegie Mellon University, suggesting both happy and sad emoticons. Given that they've made it into the blue screen of Windows 8, it seems like they're here to stay.
Wired has a nice write-up on the first emoticons, noting that while the idea wasn't entirely new -- everyone from Morse code operators in the 19th century to Ambrose Bierce had suggested typographical happy faces -- but Fahlman's suggestion was the one that really caught on. As is often the way with simple ideas, even the original message was pretty simple.
19-Sep-82 11:44 Scott E Fahlman :-) From: Scott E Fahlman
I propose that the following character sequence for joke markers:
Read it sideways. Actually, it is probably more economical to mark things that are NOT jokes, given current trends. For this, use:
Lots of people I know use (and abuse) emoticons. What's your take on them? [Wired]