Adafruit HDMI 7"
To make the Adafruit HDMI 7" 800x480 Display Backpack - Without Touch work on Raspberry Pi, I had to make some changes to the /boot/config.txt file. Else it showed a non-readable glitchy image. If you mess something up, remember you can edit the /boot/config.txt file from another computer using a SD-card reader.
Add these lines to /boot/config.txt:
# uncomment to force a specific HDMI mode (here we are forcing 800x480!) hdmi_group=2 hdmi_mode=1 hdmi_mode=87 hdmi_cvt=800 480 60 6 0 0 0