Dune.
Weighted more towards the First and last two of the original six. No comment on the new generation of pulp.
Also...
Brin's uplift universe.....
Ken McCleod's fall revolution series.....
Any Neal Stevenson book.....
Greg Bear's Moving Mars....
Vernor Vinge's "A fire upon the deep", "A deepness in the sky" wasn't bad also...
As you can see, I'm a bit more biased towards modern Hard SF.