Arduino Forum user [mdmetzle] shared a nice tv-out library for Arduino:

I wrote a small video output library called TVout. It is completely interrupt driven to make writing things that need tvout easier. It runs on a resolution of 128×96 with some basic text printing and line and dot drawing for now.

video and spec after the break.

New release:
added PAL support (my tv detects the signal as 576i anyway).
start_render(_PAL); or start_render(_NTSC);

made a few necessary changes that will facilitate future sound support and or polling UART/SPI/ect.

added a delay_frame(#frames) function to regain some semi accurate delay. this will block the user code until the end of the visible screen so it can be used to wait for a frame render to occur.

added ability to pause the display rendering but keep outputting a sync  signal(Hsync only) so user code can have full access to the cpu.

I also did some quick calculations and running as it(128H pixels by 96V double height pixels) is there is about 3.6MIPS left for user code.

updated NTSC demo (there is an included pal example too)

The massive use of interrupt may limit its use.  Nice one anyway [mdmetzle]

via [Arduino Forum]