Keys

I assume you are talking about TF2, there is no way to get them as a drop. I personally have never seen them on sale but market some times has them for cheap.

1$? Where??

$1? WHERE? :O
edit: ^ninja'd my comment.:/

1$? Where?! :|

I think he is talking about bundle keys.......humblebundle.com is your answer.

Edit: "people use them to trade for games on steam trade"......ok he isn't.

"A lot of people talk about them" mystery mystery, where is Scooby Doo? :D

oh okay so they're 2.50 each, that solves half the mystery xD

The only freeish type way I can think of in getting a key for free is through tremor games although this means doing all this watching adds, doing surveys or playing flash games stuff to get coins.