Yesterday I told you I had NTSC working on a Rev A version of VGATonic. Today, I cleaned up the code a reasonable amount and posted it on Github.
Remember: only use it with a Rev A board, even though I happily announced a new-and-improved B the other day: that one has NTSC signals broken out, but you'll need to populate the connector on the rear side of the board and (here's the kicker) build a DAC. Rev A has all of that.
Also, remember it's locked at 320x240 in 16 colors with the firmware I posted, although the code has comments in the places you'd have to adjust to increase (or decrease) colors or resolution.
Finally, don't use SPI over 21.9 MHz.
If you build a Rev A and get NTSC working, let me know! Next up: I'll take a shot at an alternate firmware for 800x600, using that shiny new Rev B board.