Format Factory is a great freeware program.
It can convert many kinds of videos, audio, data/music CD/DVDs, Pictures, and even videos compatible with mobile devices.

It can convert videos into audio.

New versions have more formats- so many, I can't add them all as tags!

IrfanView is a fast and compact image viewer/converter.
It is trying to be simple for beginners and powerful for professionals.
Many supported file formats and features.
Features include:

multi-language support, Thumbnail option, Painting, slideshow, toolbar skins, fast directory browsing, batch conversion/editing, multipage editing, file search, change color depth, scanning, cut/crop, IPTC edit, capturing, lossless JPG operations, effects, ICC support, EXE/SCR creating, many hotkeys, command line options and plugins.