I designed a NTSC/PAL Arduino Video Display Shield.
This board provides an analog composite video display with integrated frame buffer memory accessible through SPI bus. PAL and NTSC output formats are supported, possible resolutions are from 320x200 with 65535 colours up to 720x576 with 4 colors. Currently, 2 resolutions are implemented:
NTSC 320x200 with 256 colours (40x25 characters text mode)
PAL 300x240 with 256 colours (37x30 characters text mode)
A 2Mbit SPI FLASH memory is available on-board to store font character bitmaps or graphics.
It is designed for the Uno, using the board with an Arduino MEGA or DUE works, but requires a special cable or a Soft-SPI core.
Full disclosure: I am selling this board on Tindie.
Design files and software is available on Github
Some demo pictures and video:
256 Colour palette
Edit: Added "NTSC/PAL" to subject line