This page tries to collect some useful patches for FFmpeg that didn't make into SVN for some reason or another.
native Zlib decoder by Mans Rullgard
In the same thread, there are patches to use the native decoder in several FFmpeg decoders.
WMV3 encoder by Denis Fortin
H.263 rtp patch
http://www.voxgratia.org/bin/ffmpeg-0.4.7.patch.zip, originally at http://www.salyens.com/downloads/index.html#ffmpeg-0.4.7, now removed.
Apple RPZA encoder by Todd Kirby
- Jai Menon is currently working on this task as a qualification for Google SoC 2009 --Ce 04:04, 24 March 2009 (EDT)
Test Pattern Generator Demuxer by Nicholas George
Test Pattern Generator Demuxer by Ramiro Ribeiro Polla
PES packetizer by Xiaohui Sun
Part of the work of Summer Of Code TS Muxer
vf_imlib2: a libavfilter filter by Víctor Paesa
File concatenation by Wolfram Gloger
"mem" file protocol by Lagrange Multiplier
The "mem" protocol simply uses RAM as a source for input multimedia data, akin to how the "file" and "pipe" protocols use filesystem files and pipes as sources.
Presets/profiles for usual targets by Panagiotis Issaris
Allow to keep in a text file groups of command options, and apply them at once by specifying the target name.
Handy for iPod, PSP, or any other picky multimedia player that otherwise requires lengthy command lines.
See this post  to see what is missing to get it into SVN.
Electronic Arts Formats demuxer/decoder by Peter Ross
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2007-October/036919.html The format demuxer modifications and the EA video codecs have not yet been applied to FFmpeg.
Experimental MSVC port by Ole André Vadla Ravnås
OAH Build System https://launchpad.net/oah
H264 encoder by Jori Liesenborgs & Panagiotis Issaris
DTS/AC3 in wav autodetection
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/49812/focus=49909 Clean up this patch and also add detection of AC3 in wav, it is similar. Samples for both can be found here: http://www.sr.se/cgi-bin/mall/artikel.asp?ProgramID=2445&Artikel=739973
Bink Audio decoder by Peter Ross
G722 decoder by Chas Williams
This patch has no licensing issues, but also contains an encoder which was basically rejected by the project maintainer.
It might be enough to resend the decoder alone to get it into svn.
Chinese AVS video encoder by Stefan Gehrer
Lossless msmpeg4v3 to mpeg4 transcoder
Fixed point cook decoder
GDI screen grabbing for Win32
There are two implementations in the thread above.
RealAudio SIPR @16k decoder and demuxer by Vladimir Voroshilov
Expected to work with FFmpeg r15192. Ask Vitor if you want an WIP improved version of this patch.
Proper parsing of DTS-HD MA streams
ACELP.net and G.729 decoder by Vladimir Voroshilov
MS Video 1 encoder by Kostya Shishkov
LucasArts SMUSH demuxer and decoder by Kostya Shishkov
MPEG-4 ALS encoder by Justin Ruggles
libaacplus and FFmpeg encoding patch
CAFF demuxer by Justin Ruggles
This is 2 years old and not that great, but it could be a starting point at least. http://ffmpeg.pastebin.com/f21af2d03
Bayer RGB decoder
http://lists.mplayerhq.hu/pipermail/mplayer-dev-eng/2008-March/056719.html rejected in scaler, needs to be in lavc. author might be working on it...
Chromium security patches
Security/stability patches from Google's web browser http://src.chromium.org/viewvc/chrome/trunk/deps/third_party/ffmpeg/