Timothy Zahn as mentioned earlier has clean books except for triplet, and angel mass. His star wars ones are all good and I enjoyed the Icarus hunt, spinneret, and dead man's switch(could be considered a bit dark though) as well. I thought the night train to rigel was good, but somewhat boring at times. The green and the gray was good. There are some mild swear words in his books.
Battlefield Earth by L. Ron Hubbard has some mild swearing in it and is essentially clear of sex with the exception of one paragraph where the main character wonders what some natives are doing over by the sea shore and then wishes he had not looked (implied is what they were doing, while not described, so maybe they weren't doing anything

Stay away from his other books though, tons of sex and implied sex in everything else I have read by him.
Space Prison by Tom Godwin is an ok read if you are in the mood for older sci-fi and you can get past the first couple of depressing chapters.
Star Wars: Knight Errant by John Jackson Miller and his short stories except for the last one are all clean.
The Colors of Space by Marion Zimmer Bradley - an older scifi novel I enjoyed and was also clean.
Lost Tales of Power By Vincent Trigili - Wizards in space, transdimonsional wizardry, and more wizardry.
Michael Vey: The Prisoner of Cell 25 by Richard Paul Evans - Gripping.
Odyssey One, Evan Currie - No sex but so many F words, S words, and such I felt like I was in the Navy again...
Leaning more towards fantasy but might be considered sci-fi(in a very very loose sense):
Artemis Fowl series by Eoin Colfer - mild swearing but very good
Fable Heaven series by Brandon Mull - clean
Reiyalindis by Cory Poulson - I almost did not read this because the cover has a picture of a young female elf child. Glad I did though very good. (somewhat violent so don't give it to your young daughters without reading it first!)
Adventurer's Wanted: The Horn of Moran by M. L. Forman - The main character might be a bit too perfect, but still a fun read
And for a bit of techno-fi look at the Alex Rider series (though there is a decent amount of swearing and the author clearly bashes governments and spy agencies).