Well Rested

Well Rested is a status effect that grants the player a +10% experience boost for 12 hours after sleeping in a bed you own in Fallout 3 and Fallout: New Vegas.

Fallout 3
The Well Rested-effect is obtained by sleeping in a bed you own (in your Megaton house or Tenpenny Tower suite, a rented bed, or a cot in Kenny's Cave).

The perk Deep Sleep, available with the Broken Steel add-on, enables you to get this status by sleeping in any bed, but only for 8 hours.

Fallout: New Vegas
Like Fallout 3, the effect is obtained by sleeping in a bed you own (e.g. in your Lucky 38 presidential suite or Dino Dee-lite motel room) or sleeping with certain characters like Sarah Weintraub, Red Lucy, or Joana at Gomorrah.

There's also a queen bed in the bungalow in the last row of Jacobstown, which gives the Well Rested bonus when slept in.