Hmm... only on Everything2 could you find the first writeup on Light Speed to be a lyrics post (which seems to have been zapped) and the second to be a cartoon datum (which also seems to be a lyrics post). I will continue that dubious tradition. ;)
Parallel to its scientific meaning, 'Light Speed' is a generic science fiction term for extremely fast travel. However, most occurrences of so-called 'light speed' in fiction are actually much much faster than that, based on the travel times the authors use. Especially egregious is Star Wars, where the 'jump to light speed' moves them tens of thousands of light years in mere hours.
Some authors are good about treating Light Speed as being cosmically slow. These include but are not restricted to Isaac Asimov (who would guess otherwise?) in Nemesis, Ursula K. LeGuin in the world of her Hainish Novels, and Orson Scott Card, who took the same basic technologies (and others) for his Ender series, Larry Niven in The Mote in God's Eye, and no doubt many others.
If you'd like to point out anyone else who has handled this well, /msg me. If you think it's worth the effort to compile a list of those who have not, go ahead...