If it was a "good" invention, (like the car engine that gets 200 mpg) I like the flood the internet suggestion. These days, it really IS possible to get information out so quickly that nobody could stop it, even if you are into all the conspiracy theories.
If it was a "dangerous" invention, I'd say sit on it and try very very carefully to sell it to an organization you "trust." Dangerous would be things like free electricity, humgoid bombs, super growth formulas that create 50 foot tall cows, etc. ;-)
If it was a time machine, stock market predictor, and/or invisibility ray - PARTY, PARTY, PARTY.
