Her most well known sci-fi novels are probably the Left Hand of Darkness, Winter, and The Dispossessed. They are well summarized in the obituary. If you prefer fantasy, she wrote The Wizards of Earthsea series as well.
Le Guinn explores social and political questions overlooked by those who came before, and has had a profound impact on those who came after. The recent Hugo winner Ancillary Justice was heavily inspired by Winter, for instance.
Winter? That's not a novel of hers... do you mean the short story Winter's King?
Anyhow, the Left Hand of Darkness and the Dispossessed are great books. I actually didn't get into the Wizard of Earthsea for some reason, but this was probably a problem with my teenage brain; I need to go back and give it another chance. I'm also very partial to her short stories, with The Birthday of the World containing several of my favourites.
Le Guinn explores social and political questions overlooked by those who came before, and has had a profound impact on those who came after. The recent Hugo winner Ancillary Justice was heavily inspired by Winter, for instance.