Audacious' Scrobbler plugin can be configured to use an arbitrary server as of version 2.0

Audacious 3.4 comes with a new scrobbler plugin and doesnt work with libre.fm by default, if you know how to compile you can get a patch to modify the new plugin for use with libre.fm at http://jonash.se/code/librefm_audacious_scrobbler.patch