I found the Gap Cycle rather good http://en.wikipedia.org/wiki/The_Gap_Cycle

and really quite enjoyed http://en.wikipedia.org/wiki/The_Nights_Dawn_Trilogy

and found pretty much everything in http://en.wikipedia.org/wiki/Revelation_Space_universe to be as good as anything I've read by Heinlein, Clark et al.

Honestly, there's tons of good stuff out there, but it's just hard to separate it from the pulp. With the oldie goldies it's relatively easy because we have a few decades of people assessing those books.