• Perry Rhodan.

That's a HUGE series (in fact there are several series). Several hundred volumes. It's a german series, the french translation is at volume 277 (one volume = 300 pages) this month and we are almost 30 years behind the original... That's not the best written series, but it has everything: time travel, space jumps, inter-galactic travel, mutants, strange races of all kinds. To give an idea of the scope of it: from the 1st to the 277th volume, 1600 years have passed.

• "The mote in God's eye" by Larry Niven and Jerry Pournelle. Followed by "the gripping hand".

A good story about humanity's first encounter with an alien race.

• The Heechee saga (Gateway, Beyond the Blue Event Horizon, etc) by Frederik Pohl

Humanity's encounter with a very advanced but abandoned (?) technology.

• Ringworld by Larry Niven

Several books about the HUGE ringworld: several of worlds in fact set on an enormous artificial ring stucture in space and the mistery of its creators.

• the Uplift series by David Brin.

Several books where humanity struggles against a rigid galactic system in which they are newcomers & not always welcome. The depiction of alien races is especially good.

• Angelmass by Timothy Zahn

The Angel is a particule that forces people to act ethically. But not everybody agrees and greed threatens to bring war. A bunch of unlikely heroes find themselves engulfed in a space-wide struggle that goes far above their heads.

• Many older good novels/short stories can be found as eBooks, look here: http://www.feedbooks.com/books/top?category=FBFIC028000&lang=en&range=week

Look for Leinster, Piper, Norton, Harrison, Philips, Garrett, Smith. There are many others.