Ben Bova's "Planets" novels -- "Venus", "Saturn", etc.
Stephen Baxter - Pretty much read all of his stuff, but there are a couple left to go. If you have to start with one of them, pick 'Timelike Infinity" or one of the "Manifold" books, like "Manifold Time". Bugger those. Instead, read "Ring" first. Why have dark-matter based giant space birds been smashing galaxies together for billions of years?
Oh, wait. Try "The Light of Other Days" - Imagine a WEBcam that could not only open a tiny (undetectable) wormhole to anywhere, it could open one up in any time. Privacy? Schmivacy.
Robert Jordan - The Wheel of Time series - What, me read fantasy? What up, Dawg? Careful, there are 10 books in the can and perhaps the 11'th being published as I type this. I've read four, but I bought 10 of them at Half Price Books.
Greg Bear - EON