In addition to the official plugins, there are many other open source and commercial plugins listed below (in alphabetical order) :

Open source

gladstone

GladSToNe is an educational tool for learning about hi-performance audio handling for real-time transmissions. The goal of the project is to use the open source model to improve the psycho acoustics, noise shaping and speed of audio transmissions over IP. Contains a G729 codec plugin, g729enc for encoding and g729dec for decoding.

• Project page on Google Code
• Code repository on Gitorious
• Profile on ohloh.net

gst-buzztard

Extra interfaces for audio plugins + a few plugin using them. Contains a wrapper for buzz-machine plugins. audiodelay add an echo effect to audio, the bml plugin wraps buzz-machine plugins, fluidsynth is an audio synthesizer, and simsyn is a simple monophonic audio synthesizer.

• http://buzztard.svn.sourceforge.net/viewvc/buzztard/trunk/gst-buzztard/

gst-fluendo

Fluendo provides several open source plugins, including:

• an MIT-licensed mp3 decoder (flump3dec)
• an MPL-licensed MPEG Transport Stream and Program Stream demuxer (flutsdemux, flupsdemux)
• an MPL-licensed MPEG Transport Stream muxer (flutsmux)
• an MPEG TS Timeshifter element (flufakeshifter for time shifting on fake streams, and flumpegshifter for time shifting on MPEG TS streams)
• an MIT-licensed iLBC decoder / encoder (fluilbcdec, fluilbcenc)
• an MIT-licensed ADPCM decoder (fluadpcmimaqtdec, fluadpcmimadvidec, fluadpcmmsdec)

• an LGPL-licensed GDL sink for Intel's Sodaville and Canmore platforms (flugdlsink) The code and issue tracker are hosted on Fluendo's TRAC:

• https://core.fluendo.com/gstreamer/trac

gstlal

A suite of elements for gravitational-wave data analysis from the LIGO project.

• Project page - including Git repository

gst-plugins-elphel

Elphel camera-related plugins, including jp462bayer which converts color and monochrome JP46 Elphel bitstreams to Bayer raw format, and bayer2rgb2 which converts raw Bayer streams to RGB images using libdc1394 debayering algorithms.

• Project page on Google Code - including SVN repository

GstStabilizer

Python plugin using OpenCV to stabilize video.

• https://github.com/guijemont/GstStabilizer

PiTiVi

http://www.pitivi.org/ PiTiVi is a Python-based non-linear editor, and includes several Python plugins

• repository browser

pocketsphinx

Speech recognition plugin based on CMU sphinx. pocketsphinx takes audio as input and produces text on output, and vader marks utterance start and end points in an audio stream.

• Using PocketSphinx with GStreamer and Python (or Vala) - includes example code
• SVN repository on Sourceforge

Commercial

• Entropy Wave codec package