When I ran my Futura (SF RPG) game
I would have lots of Heavy Metal and Epic magazines around and let people look through them before and after play (some times during play).
It helped keep the mind set of what future/alien world might be like. One game a character decided they wanted a better alien pet than one of the other characters (keeping up with the jones

and started looking through the mags for what they wanted. It ended up being a long adventure.
When ever some one said that they would like to play a future/scifi game but wanted to know what kind of game mine was, I would reply
What do you want to play in a science fiction game?
I would work with the new player and we would come up with a character and what that character wanted out of life (at least the following goals, short (1 yr), long (1 to 10 yrs) and achievement before death).
Then I would do some research (game systems, books or just make it up based on our decisions) and figure how to add that character to the mix of players.
Many players had at least 2 different characters so that we could be in the middle of one adventure and they could start with an other adventure with different players.
( I had over 50 actual players involved in my game over the course of 3 years.)
The largest group at one time was 22 players in the room playing at the same time. (wow, it was a blast and I had to miss 2 days of classes to recover
Basically I like all the responses.
I believe that trying to describe Traveller in general is good BUT if you are trying to get players to play in your game of Traveller make sure that you describe your universe.
When I worked for a game company we used the term flavor of the game.
Before MK: Dungeons was released (and before I worked for WizKids LLC) I was able to demostrate MK: Dungeons at GenCon by having the players concentrate on the feel of the Heros running around in a dungeon and only made them use the basic MK rules that applied to figures.
The point behind this is if you ever get a person interested in a game (SciFi) or Traveller and they want to know what it is like or how it is different, Take a bit of time and talk/roleplay with them in a what if you were X character from Y movie or book (one that they have seen or read).
Ask them if they have every caught a ride with some one to some where, if yes ask them what they think it would be like to walk down to the nearest starport and hitch a ride on a space ship.
In a nut shell, Traveller is the vehicle to allow the refree/game master to aid in telling an interactive story involving other players. I like Traveller because if you want aliens you have them, if you don't want aliens the universe if big enough that the players could never run into let alone see one.
If you want High Tech or Low Tech it is there. If you want Techno Mages or Ancients it is there.
Most other games have a limited scope to make it easier to play and grasp. Traveller is easy to grasp but has lots and lots of room for details (I.e. refree has lots of work to do to the more detail that you want.
So much for a short post.
Dave