Hundreds of emoticons have been proposed, but only a few are in common use. These include:
:-) `smiley face' (for humor, laughter, friendliness, occasionally sarcasm) :-( `frowney face' (for sadness, anger, or upset) ;-) `half-smiley' (ha ha only serious); also known as `semi-smiley' or `winkey face'. :-/ `wry face'(These may become more comprehensible if you tilt your head sideways, to the left.)
The first two listed are by far the most frequently encountered. Hyphenless forms of them are common on CompuServe, GEnie, and BIX; see also bixie. On Usenet, `smiley' is often used as a generic term synonymous with emoticon, as well as specifically for the happy-face emoticon.
It appears that the emoticon was invented by one Scott Fahlman on the CMU bboard systems around 1980. He later wrote: "I wish I had saved the original post, or at least recorded the date for posterity, but I had no idea that I was starting something that would soon pollute all the world's communication channels." [GLS confirms that he remembers this original posting].
Note for the newbie: Overuse of the smiley is a mark of loserhood! More than one per paragraph is a fairly sure sign that you've gone over the line.