15mm science fiction (Stargrunt II, specifically) was one of my starting places in miniature wargaming; I don’t do much these days but I still have all my figures and I still keep an eye on the field. These are great days for 15mm SF gaming, with a bunch of new companies involved with rapidly expanding ranges, as well as new stuff from established companies like Ground Zero Games.
I used to maintain a long page of companies involved in 15mm SF – many people still link to it, so you might have followed a link expecting to find it, but I’m no longer as heavily involved in that scale & genre as I once was, so I’m going to refer you to Dropship Horizon instead. Dropship is an excellent blog devoted almost exclusively to 15mm science fiction gaming, and even better, on one of their right-hand sidebars they have a long list of 15mm Sci Fi Manufacturers!
Dropship also has news and reviews of the latest and shiniest stuff from those manufacturers, some neat projects of his own, and a good group of commentators to boot. Go check it out!