I loved The Forever War by Joe Haldeman, recommended previously in this thread, and that got me to Old Man's War by John Scalzi. (It might be interesting to note that Ridley Scott has hold the movie rights to this book for many years now. I can't see it really becoming a mainstream movie without cutting out some themes from the book.)
The theme in Old Man's War are sort of the same as The Forever War, but in such a minor way that it didn't bother me even once. Scalzi then turned that book into a series, all very well worth reading (except Sagan's Diary - give that a miss). After his Old Man's War series I read Redshirts (so and so), Agent to the Stars (good read) and now I'm reading Fuzzy Nation, which is shaping up nicely.
In the afterword to Agent to the Stars Scalzi actually recommends other scifi books, and per his recommendation I tried out Stranger in a Strange Land by Robert A. Heinlein (of Starship Troopers fame) but that quickly grinded to a halt. Might give it another chance later.
Oh, I also read Haldeman's Camouflage. Seems to be liked by the reviews I find online, but I found it to be a waste of time due to a very weak end chapter.
After this I plan to dive into Rama territory and perhaps Dune also.
Please keep the book recommendations coming, this thread is a goldmine. :)