Dragonfly,
I will tell you what worked best for me when introducing 6 of my friends to Traveller for the very first time.
For the very first adventure, make it the last mission of their last term of their character generation.
Normally when you make a character, you simply roll dice and see what happens. On your final term you muster out, buy gear, then start the adventure. You meet at the proverbial "space bar" and ask... "who wants to go adventuring?"... ok... maybe not like that, but it's pretty close.
In stead, create an short adventure for your characters last mission. Since this adventure is "technically" part of their background / character generation, you as a GM can have a certain amount of leeway with the story line. I will tell you how I handled it.
All 6 of my friends were part of the same crew of a large merchant cruiser called "The Leviathan". It's a ship that appeared in one of the old adventures back in the early 80's.
Since they were all part of the crew, they already knew each other for several years, no awkward... hm... my names Bob, and I'm an adventure... wanna go kill a dragon??...
Anyway, their mission was to rescue the CEO of a manufacturing facility on a corporate moon. The owner of the Leviathan has a contract with the corporation in question, so they get to do the dirty work. Once their ship jumps into the system, they are attacked by a few small pirate/merc ships (hired by the bad guys who are sacking the moon facility), so a short space battle starts. This space battle is simply a tool to teach the players (and the GM) how space combat works. As a GM you "allow" the crew to win. (remember this is the characters background creation, so don't kill them). In my case, my friends got to use their pilot skills, (one flew a fighter), targeting, tactics, comms, and any other skills that could be used in a space combat. After they chase off the smaller ships your characters insert themselves into the company town surrounded by factories etc... The best situation is to let your players with "Ships boat" skill fly the 20 ton "special ops launch" down to a designated landing site. Launch missiles and energy weapons at them as they descend.
In my case I "pre-programmed" my players launch to get shot out of the sky, the pilot rolls "just good enough" to crash land in a small plaza. The players survive the crash, but in my case, their NPC leader (Lt. Dan... he looses his legs...) dies in the crash, so the player are now on their own to locate, rescue and find another way off the moon with the CEO. In short, my players found the CEO, killed the bad guys, stole another small launch, and escaped back to the Leviathan. This "adventure" allowed all the players (and GM) a variety of situation to test out their skills in several combats, recon, roll-play, and just fun. It got everyone used to the system, allowed questions, and find solutions.
After they got back to the ship, they were all congratulated on a job well done. The Leviathan went on it's way to its final destination, where my players finally finished their contract. That's when their "rolling up characters" ended, they mustered out, and got ready to begin the "real adventure" the following weekend.
They all really enjoyed the idea to get one night of adventuring under their belt "that didn't really count", so they really couldn't screw up too bad. It was all one fun exerciser in how to play the game, and a chance for the players to get to know each other. My characters decided to put all their ship shares into a specially designed 300 ton armed merchant. They are now enjoying my on going campaign for the last few months.
Everyone else before me has given you plenty of ideas for an ongoing adventure...
Oh... one note. I DO have a Zho psion in my group. He created a character that discovered the "truth" behind the absolute control of Zho psions have on the Zho non-psions, so he fled into the Emperium. He finished his pison studies withing an underground institute. So far, he has done a good job on hiding his talents from those who would turn him into the authorities.
Hope that helps