I think that at this point, if there was an easy, free way to promote the game, Toonces would have done it by now.
We can post as many fake reviews on gaming sites as we want, but if no one's googling 'Starport: Galactic Empires' anyway it doesn't really matter.
Best I can think of would be to advertise on another mainstream website like facebook, but once again, if toonces was interested in doing it, he would have already done it by now. However I do think that it would pay off in the long term. Even shitty games have thousands of people playing for them, and paying for them, just because of advertising. And since SGE isn't complete BBQ yet (we're still here, at least on the forums, right?), the players the ads bring in would at least end up paying for them.
One of the great things about SGE is it looks so cool as a newbie. Couple that with the options in the admirals club doubling in quantity and the cost of ads to bring in a surge of players should pay for itself and then allow for some expansion.
Hey it's just an idea.
Another thing we could do would be to muster as many people as possible at one time (maybe 100 if everyone liked it?) and just spam SGE related BBQ onto as many sites as possible. Even 20 people constantly spamming A mainstream youtube song might get some attention. who knows.
To answer your question major, aside from anything risky (ads) or desperate (spam), I don't see an economical, effective way of promotion. Maybe if a lot of people put in a lot of time we could think of and implement something, but who the hell wants to do that?
In short, there's no easy way for us players to promote the game.