[Dngrsone]

I liked Chris Moriarty's Spin series, which is three books.

C.J. Cherryh, Arthur C. Clark, Greg Benford, are all good.

As are Larry Niven, Greg Bear, and Issac Asimov. These all tend toward the harder side of Sci Fi.

If you want to cheap out, then check out some of the classic writers like H.G. Wells and Jules Verne at Gutenberg (not to mention the Sci Fi/Fantasy deals of the month threads in these forums).

If you like Cyberpunk, then you can't go wrong with Neil Stephenson.

I have read and enjoyed the Dan Simmons' books mentioned, as well as Kim Stanley Robinson's trilogy (good choice there) and the Honor Harrington books by Weber. The last few didn't sit as well with me as the first four or five, though... it seems like he's trying to milk it out or something.