The DES (the data encryption standard) is being replaced.
In an article on CNET, Bruce Schneir, a well known author in Cryptography, has written about the DES and its uses. He talks of how it was modified by the NSA and how a new algorithm is being put in its place.
Bruce Scheier's books, Applied Cryptography, is particularly good. Its not a read for the layman, as it does get quite technical. In the US the book comes with a disk which contains the source code for the algorithms in the book - this was banned from export, although the book itself (which contains the algorithms) was not.
Wikipedia has a 'Project Cryptography' available which may well be worth a look. Bear in mind with wikis, anybody can edit them. So long term, information tends to be reasonably reliable if the thing is maintained, but in the short term things might not be.