My absolute favourite piece of sci-fi is the webcomic A Miracle of Science [http://www.project-apollo.net/mos/index.html]. It has mad scientists, sapient robots, the only large-scale (spanning the entire planet of Mars, which appears to be quite well-populated) group intellect I've ever seen that wasn't evil and/or a sinister entity depriving its members of individuality, and for the most part sticks to the real-life laws of physics and avoids the gaping plotholes you see in a lot of sci-fi (for instance, potentially versatile technology only being used for one task). It was written by a guy who knows a lot of real-world science, so the annotations are also quite informative.
I also quite like Ender's Game, Firefly, Transmetropolitan, HHGTTG, Dune (although I never did read the last two books... and, come to think of it, it's been years since I read any part of the series), Doctor Who, and the second segment of 2001: A Space Odyssey. Haven't read much Asimov beyond one standalone book, but I did like Nemesis, and I've heard a lot of good things about the rest of his body of work, so I should probably check it out.