Greg Bear's EON and Legacy. Both set in the same universe and have some key characters in common but related to totally different events. There is a sequel to EON but it's unremarkable though it has some interesting ideas and other people seem to like it.

Greg Bear's "Forge of Gods" and "Anvil of Stars", the former is (together with Jack McDevitt's Moonfall) clearly the basis for some key plot points in Deep Impact, Armageddon and 2012. But the movies just cannibalised the excellent books and turned them into crap, and are not in any way indicators of the book's quality. The Anvil is a sequel to the Forge and is breathtaking in its scope and execution. Talking about global calamities - Baxter's "Moonseed" is also a good one.

Vernor Vinge's "A Fire Upon The Deep" and "A Deepness In The Sky", just pure distillation of scifi genius and both a Hugo winners.

Finally, I would add Ben Bova and his "Grand Tour" of the Solar System - an interesting series with some imaginative plots. I was not overawed by the Moonbase but the rest is quite good. This can be well complemented by Baxter's "Voyage" and "Titan" but he is a bit too downbeat for my liking...