Tara's Note is a paper note in Fallout 3 which was cut from the final version of the game. It can only be obtained via console commands.
If anyone finds this note, stay the hell away from this place. If the feral ghouls don't get you, the robots will. There's radiation everywhere. I think they used to make nukes here, or maybe they just kept them, I don't know.
This note, along with Dave's note, Dukov's note, Mister Crowley's hit list and Strayer's note, are apparently a leftover of earlier versions of the quest You Gotta Shoot 'Em in the Head.