A great resource for finding wonderful SF is to check out the winners and finalists for the major awards. For example, here's a list of the John W. Campbell Memorial Award winners. And here's a list of recent finalists for the Award.
Here's the list of the Nebula Award novel winners.
And the Hugo Award winners, which has links to each year's finalists, as well.
So much good stuff out there! A couple of books I didn't get a chance to mention include Bradbury's R Is for Rocket which contains a story that turned me into an author: "The Rocket" (along with Heinlein's Rocketship Galileo and L'Engle's A Wrinkle in Time). Bradbury's Dandelion Wine is another, along with books like Herbert's Dune, Adams' The Hitchhiker's Guide to the Galaxy, Simak's City (a Minnesota native), SF anthologies like James Gunn's Road to Science Fiction and the DAW Annual Year's Best SF, and tons more.
My favorite Bradbury short story is pretty much everything Bradbury every wrote. His writing is moving and evocative like Simak and Sturgeon's - probably why those three made such an impression on the young-me. But if I had to pick only one that most influenced me as a writer, it would probably be "The Rocket," a beautiful story about a junk-man who has to decide between his personal dreams of space and love of his family. It was adapted into a radio show for NBC's "Short Story" series (you can listen to the MP3 audio recording here).