Larry Correia (I’m waiting for his ripping on this) has some sci fi stuff, he’s freedom loving, mormon too but I dont hold that against him. Baen Books has several authors that are conservative, libertarian bent, but they are freedom of ideas so they have some lefty authors too—some are good too.
S.M. Stirling is my favorite Baen author.
The Draka series is intense.
I expect Sarah Hoyt will weigh in on this in her blog: www.accordingtohoyt.com
She generally writes with a libertarian perspective.