Should DES be avoided when developing new systems? According to wikipedia…


  DES is now considered to be insecure for many applications


However, since it can be broken relatively easy, should it not just be avoided for all applications?
Yes. DES is no longer considered an approved algorithm by NIST, and breaking a 56-bit key can be done quickly - in 1998 the EFF DES Cracker managed to break a DES key in 56 hours. The average time it required to break any DES key was 4½ days. You could use triple DES instead, which is still considered secure, but it's very slow (in software, even single DES is slower than AES), and a time-memory tradeoff described by Martin Hellman in 1980 shows how to break 3DES with a 168 bit key in $2^{112}$ time. In addition the 64 bit block size is a major practical problem if using 3DES in some modes, as described by Thomas in his answer.