The Federation Crash Site is a special encounter in Fallout 2, consisting of a shuttlecraft (christened the U.S.S. Torres) half buried in the dirt and three dead people, wearing strange red uniforms the player character has never seen before. These people are dead from dehydration. They also carry futuristic-looking hypodermics, which are essentially super stimpaks that are free from the HP-loss-after-time side effect.
There was also supposed to be a Phazer that can be obtained in this encounter, but it was removed.
The whole encounter is, of course, a reference to the science fiction franchise Star Trek. The shuttle is virtually identical in design to those of the U.S.S. Enterprise from the Original Series, and the redshirts are the (in)famously ill-fated characters introduced simply to get killed by the episode's monster-of-the-week.