Known Open File Types

(note, open file types are not necessarily defacto file types. If there exists freely available source code
without patent violations, then the format is open)

This list is far from complete

Audio

wav
au
mp3
voc
snd

Image

gif
tif
jpg
PIC
XBM
PBM, PGM, PPM, PM
PCX
TGA
XPM
GEM/IMG
IFF/ILBM
BMP

Video

mpg
dat

Text data

txt
html
sgml (DocBook)
dvi
ps
tex

Archive/Compression

gz
zip
zoo
tar
ar

* note, there exists mixed types as well. Animated GIF's and grap gl's are examples of these.
I would classifiy these under image types, not video types. But that is debatable.