In this final installment of the "Helpful Links" series, I'm listing several good places for searching for, finding, and ordering books. You'll see my Reformed preferences coming through loud and clear.
Banner of Truth - This is an excellent place to find historic Christian books, especially those from the Reformation and Puritan eras. A great place to start is the Valley of Vision, A Collection of Puritan Prayers.
Crossway - Go here to find a wide variety of Christian books, tracts, and ESV bibles.
CVBBS - Click on Cumberland Valley for various Reformed-perspective Christian books.
Monergism Books - Closely related to the Monergism website, the bookstore offers many different Reformed selections including commentaries, church history, apologetics, etc.
RHB - The purpose of RHB is to "glorify God and strengthen His church through the publication and distribution of Puritan and Reformed Literature." My favorite RHB selection is entitled "Meet the Puritans, With a Guide to Modern Reprints."
Westminster - At the bookstore for Westminster Theological Seminary, you will find exactly what you would expect from this excellent theological school - solid Christian books of all kinds.