For C/C++, I heartily recommend C: The Complete Reference It is what is says: a complete, no-nonsense reference to C with all the information you'll ever need, and none you don't, organized with impeccable logic and pragmatism. Herbert Schildt's C++ tome is quite worthwhile as well.

Please, please don't recommend Herb's bad books on C. They're written simply, yes. They're also written simply wrong. I refer you to ##c/Freenode's wiki stating why.