I've implemented the "Kölner Phonetik" algorithm (cologne phonetic), which is a phonetic algorithm optimized for the German language. For a German description see: http://de.wikipedia.org/wiki/K%C3%B6lner_Phonetik . For an English description see the source-code comments.
If you want to add the following classes to commons-codec, feel free to adapt the sources to your guidelines and needs.
Latest source files (I wasn't able to attach files):
org.apache.commons.codec.language.ColognePhonetic - http://ubuntuone.com/p/Fzm/
org.apache.commons.codec.language.ColognePhoneticTest - http://ubuntuone.com/p/Fzn/
See also thread "[codec] Kölner Phonetik (cologne phonetic)" at email@example.com (firstname.lastname@example.org)