For C++98, the standard everyday reference work for the C++ standard library was Nicolai M. Josuttis' The C++ Standard Library. His updated version for C++11 has been eagerly anticipated, and I was pleased to receive my copy yesterday.
Interestingly, the physical size of the new book is no larger than the original edition, even though the standard library has become a lot bigger. The new book has 300 more pages, however. (Exactly 300. The final page number in the first edition is 799, and the final page number in the new version is 1099. How he managed that, I don't know, but it's a neat trick.)
[The following information about electronic editions has been revised since my original post.]
In terms of electronic editions, the book is available in PDF and ePub, plus there is an edition for Kindle. This information is courtesy of comments readers left on this blog entry, and I am grateful to them for it.
I encourage you to consider buying your own copy of the new edition of The C++ Standard Library. Having it close at hand was indispensable for C++98 programming, and I think that having it close at hand for C++11 programming will be just as important.