Here's a neat list that I found on ugo.com. Is your favorite on the list?
"Extra-terrestrials, supersonic spaceships, futuristic robots, cloning experiments: these technological ideas and intelligents beings all pale in comparison to the skimpy sci-fi costume. To celebrate the hottest sci-fi girls of all time, we've collected the most interesting and influential specimens from this side of the galaxy and tried our best to rank them based on character, movie and overall hottiness. Yes, some ladies didn't make the cut (we miss you Orion Slave Girl), but we think you'll appreciate the balance of new, old and quirky. Just remember, hot isn't only about the way they fill out their spacesuit (though it certainly helps!). So without any more dilly-dallying, come check out the Top 50 Hottest Sci-Fi Girls of All-Time!
Feature by Troy Landringan"