/usr/share/applications/

ubuntu@ubuntu:~$ apt-file search /usr/share/applications/ | awk '{sub("[^/]+.desktop$","");print}' | sort -t: -k2 -u
3dchess: /usr/share/applications/
gtkvncviewer: /usr/share/applications/data/
desktop-file-utils: /usr/share/applications/defaults.list
fte-xwindow: /usr/share/applications/fte32x32.xpm
gprename: /usr/share/applications/gprename.schemas
pornview: /usr/share/applications/Graphics/
kourou: /usr/share/applications/hildon-home/
hildon-desktop: /usr/share/applications/hildon-navigator/
matchbox-keyboard: /usr/share/applications/inputmethods/
webhttrack-common: /usr/share/applications/Internet/
cutecom: /usr/share/applications/kde/
adept: /usr/share/applications/kde4/
glame: /usr/share/applications/Multimedia/
electricsheep: /usr/share/applications/screensavers/
therion: /usr/share/applications/therion.desktop/
therion-viewer: /usr/share/applications/therion-viewer.desktop/
libhildonmime0: /usr/share/applications/uri-action-defaults.list
wally: /usr/share/applications/wally.desktop/