I've read CS Lewis. I like science fiction, but most of it is Gaia-worship, capitalism bashing, evil Christians or atheists in space. Christian sci-fi seems a contradiction, but it doesn't have to be.
I like Tamara Wilhite's writings, but she only has one book thus far.
Have you read the Science Fiction Trilogy by Lewis? It has recently come back into print.
Also there is a great deal of Christian themes in Madeleine Le Engle's Wrinkle In Time series.
If you've read CS Lewis and like Sci-fi, do I take it that you've read the Perelandra trilogy (the other books being "Out of the Silent Planet," and "That Hideous Strength") A few notes on "That Hideous Strength": Lewis loses his knack for breathtakingly sharp concision, and he deals with the natural joys of sexuality in a way that many Christians aren't necessarily used to reading about. Nothing smutty -- he doesn't invade his characters modesty by learing -- but still very sexual in a way that made me, when I first read it at 13, rather uncomfortable. (Not because I was prudish, but because it was of matters I, as befitting my age and status in life, had so little connection with.)
Ray Bradbury is another author I might offer. He has some views which might seem unorthodox (un-orthodox, if you get my drift...) and at times he seems very atheistic at first blush... but then you realize he writes from the perspective of people who have let worldliness NEARLY completely shut religion and spirituality out of there lives. Therefore, when there are unmistakable hints of Christianity alive in his worlds, there seems almost a triumphantalism about it, like that line (and I can't believe I can better think of it from Jesus Christ Superstar than from scripture, but the original POINT of song was to memorize verse better): "If every tongue was stilled, the noise would still continue; the rocks and stones themselves would start to sing, 'Hosanna'!" -- It's like in Bradbury's worlds we witness the stones singing.
It's as if from the deepest reaches of his soul, Bradbury knows of the truth of Christ, and tries to infuse it into the bleak, atheistic presumptions of cold-war-era Sci-Fi; his only flaw is that it seems he hadn't the will to explode the paradigms.
Ironically, Isaac Asimov, bitter atheist that he is, manages some amazing metaphors of Christian faith... and occasion some strangely poignantly spiritual matters. In one story, he refers to a civilization which had joy in its own destruction, for theirs was the sun that went supernova to proclaim the birth of Christ, a sacrifice they were willing to pay. (As I write about it now, I wonder if that reflects some Judaic insight.) He has several stories along the lines of "the mystics were right after all..."
The movie version of Contact is interesting also. The book was terrible... anti-religious and spending hundreds of pages exploring the sexual frustrations of Jody Foster's character. The movie turned Foster's star travels into a metaphor for religious experience. Of course, a Christian in the story is a hypocritical pompous ass, but while one tires of that being the ONLY side of Christianity portrayed in Hollywood, his character was typical Washingtonian Christian, sadly.
Madeline L'Engle is a devotee of CS Lewis and Milton, who wrote sci-fi "for children" in the way that CS Lewis wrote fantasy "for children." It's been since I was a child that I read her, and some of my vague recollections are sorta what I would now call "new-agey," yet she strikes apon some of the most powerfully expressed notions that eventually led me from fairly radical leftism to conservativism.
(Yes, I am a TRUE neo-con, by Buckley's definition. I became conservative as I recognized that liberalism was a lie and was counter-productive, because I did have a few very strong conservative values alongside liberal beliefs I inherited from my then-passionately Democratic parents, informed by my parents' strong religious faith. And yes, my parents eventually also "converted" to conservativism as the Democrats became increasingly transparently incompatible with Christian faith, and I explained to them "the truth." :^D)
I should re-read L'Engle... I'm not at all certain she ever promoted a single new-agey ethic; she certainly was anti-socialist. Even my notion that a main character was Wiccan may be a hyperlexic error based on a character named Mrs. Which, not Mrs. Witch. She was magical, but she also had friends with names such as Mrs. Whatsit, etc.