Ding is often used as a replacement for saying "That's what she said." It originated from a person ringing a bell whenever such a statement was necessary.
When talking about a test...
"Man, that was hard!" -Person 1
"*Ding*!" -Person 2
When talking about a hotel room card...
"Put it in and pull it out quickly."
"*Ding*!"
A term used in MMORPGs to signify the achievement of a new level of experience of one's character. This term was defined in the smash hit EverQuest, as the sound generated upon gaining a level sounded as a bell.
The concept trickled down to other MMO's as well, but few actually know the true origin of the word.
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.