Smashwords also has sections for these genres: Science Fiction & Fantasy:
http://www.smashwords.com/books/category/875
Thriller and Suspense:
http://www.smashwords.com/books/category/874
Some books are free, some books are paid. All of them should have a sample of some kind and come in several formats so you can try before you pay to see if you like the writers work.
...also I often write Sci-Fi, but I say Science Fiction... so did my Grandfather who was very into it. Perhaps this is a regional issue? And SF would never make me think Science Fiction off the bat, either.