Suggestions?

Neal Stephenson's new one comes out next month!
Besides that, anything by John Scalzi or Tobias Buckell is awesome and fairly recent.
'Little Brother' by Cory Doctorow just came out this year.
'The Stars My Destination' by Alfred Bester is older but so awesome.
Peter Watt's novels are really intense SF and vastly under-appreciated.
'Appleseed' by John Clute is the hardest of the hard SF and you might sprain your brain on it.
'The Reality Dysfunction' by Peter F. Hamilton is. THE. BOMB. a way epic trilogy set in space in the far future. If you are an SF fan and you haven't read it, your life is in fact not complete.
Anything by Ian McDonald if you love books jam-packed with interesting ideas and lots of action.
'Postsingular' by Rudy Rucker is amazing, and he just finished writing the sequel. Great ideas and great characterization.

Take a look at Jeff Long's The Descent. It is usually shelved in horror but it is a sci-fi story. The movie has nothing to do with this book. I think it's just an obvious title when dealing with the 'what lurks beneath the earth' type plot line. Long's book is really, really good.

I think one of the best books for you is
David Pringle's Science Fiction 100 Best Novels
It took me a couple years to read all 100, and I can recommend every one

I've just discovered Terry Pratchett. You probably already know all about him and wow am I behind and all that. But if you haven't, he's fantastic and funny as all hell. I know, he's a fantasy guy... but still. You might get a kick out of him.