The Vamp libxtract plugin set is a library of low-level feature extraction plugins using Jamie Bullock's libxtract library to provide around 50 spectral and other features.
See
http://libxtract.sourceforge.net for more details about libxtract.
A new update of this plugin set (the 20081202 update) is available fixing a number of bugs in the plugins, following a review and user feedback. This set should be more stable and useful than previously. See
http://www.vamp-plugins.org/download.html for source and binary downloads.
Chris