So I've talked about this elsewhere, but I think that it would be cool to talk about it here:
So, one of the worlds that my friends and I are building (it's actually had a few chapters posted here, under Our Vocab English Assignment (I promise you, it's better than it sounds) ) has two suns. But not in the way that say Tatooine has two suns. The suns are positioned on exact opposite sides of the planet. Basically, the two stars rotate around each other, and the planet just happens to sit exactly in between them. It's just outside both of the star's habitable zones, but because it gets heat from both stars, it still can support life. It takes a total of 42 hours to spin completely around its axis, and so there are 2 18 hour days and 2 3 hour "nights" (they're about as dark as twilights on Earth) per rotation.
It's still the pre-technology typical fantasy era, but scientists have discovered enough to know that it's not just one sun, it's two. One of the suns has a more reddish tint, and mythology has evolved around that. Basically, First Sun (the yellower one) is heaven, and Second Sun is hell. It's been interesting to write.
And yes, I am using this as a shameless plug to get you guys to read it : http://www.17thshard.com/forum/topic/20613-our-vocab-english-assignment-i-promise-you-its-better-than-it-sounds/