JSON is a format increasingly emitted by web services, being fairly lightweight, flexible, and cross-language. Bob Ippolito's simplejson is a pure Python JSON toolkit:
simplejson is a simple, fast, complete, correct and extensible JSON encoder/decoder for Python 2.3+. It is pure Python code with no dependencies. simplejson 1.5 is a major update that provides better Python 2.5 and Windows compatibility, and two new features that control encoding (indent for pretty-printing, and separators for generating optimally compact JSON)
Good to have in the toolbox!