HandBrake is an open-source, multithreaded video transcoder – it compresses and converts digital media from one format to another. HandBrake can rip encrypted DVDs with libdvdcss (libdvdcss is installed with VLC media player on macOS, or AnyDVD/DVD 43 on Windows).
FFmpeg is the leading multimedia framework, able to decode, encode, transcode, mux, demux, stream, filter and play pretty much anything that humans and machines have created. It supports the most obscure ancient formats up to the cutting edge.
File Converter is a very simple tool which allows you to convert and compress one or several file(s) using the context menu in Windows Explorer.
last update 2017
XMedia Recode can convert nearly all popular audio and video formats including 3GP, 3GPP, 3GPP2, AAC, AC3, AMR, ASF, AVI, AVISynth, DVD, FLAC, FLV, H.261, H.263, H.264, M4A , M1V, M2V, M4V, Matroska (MKV), MMF, MPEG-1, MPEG-2, MPEG-4, TS, TRP, MP2, MP3, MP4, MP4V, MOV, OGG, PSP...
Format Factory is a multifunctional media converter and DVD ripper. Its features include:Bundleware
Be careful during the installation: https://alternativeto.net/discussions/applications/11718/be-careful-in-the-installation/
ClipGrab is a free downloader and converter for YouTube, Vimeo, Metacafe, Dailymotion and many other online video sites.
The default Windows installer contains Opencandy. A version with no third-party offers is available in Download options.
Open source software without any restriction - converter all formats video|audio|image professionnals codecs and standards - swiss knife tool Windows and OSX.
Freemake Video Converter is video converter that lets convert videos to avi, wmv, mp4 (iPhone, iPod, iPad, PSP, xBox), 3gp, rip dvd, extract mp3, burn DVD and Bluray, create photo slideshow and audio visualization, cut, join, rotate and upload videos, photos and music to YouTube.
The installer contains OpenCandy. Be careful during the installation: https://alternativeto.net/discussions/applications/11718/be-careful-in-the-installation/