VoxForge
From this post:
gvc [gnome-voice-control] has just got German and Russian support. To test it you need to checkout gvc from svn trunk as well as pocketsphinx and sphinxbase from trunk. Then unpack voxforge acoustic model to ${prefix}/share/pocketsphinx/models/hmm/voxforge-de and start applet in de_DE locale. Everything should work fine, testers are welcome.