Stumped as to the encoding used in a given file or bit of string data? Mark Pilgrim strikes again with a Python library "as smart as your browser." The result includes confidence, which is a big win in my eyes.

http://chardet.feedparser.org/

Version 0.5 adds a Python binding! libextractor is a library used to extract meta-data from files of arbitrary type. It is designed to use helper-libraries to perform the actual extraction, and to be trivially extendable by linking against external extractors for additional file types.

http://gnunet.org/libextractor/