The TVout lib is one of the most useful things I've found.. I made a audio spectrum analyzer with video output:
and a light pen:
it simply provides a ton of display space for the cost of a couple of resistors.
I use it with a portable DVD player that the dvd drive no longer works on, but takes composite video input. I love it because it only requires two pins for all that functionality to boot. This was the fist video of it I put online, the screen is the DVD player screen. You can buy NTSC composite color monitors, 3-6" in size for use as backup camera monitors off ebay for under $50. Hard to beat. I suppose I shouldn't use AC/DC, but rather appropo music imo...
Sure it's a memory hog and all that, but it's so dang useful, I consider it one of the best Arduino libs out there! I suspect it may be a different story under a Mega or a 1280.. it's the memory for mapping the data that is the problem. Bit mapping even monochrome:
Memory=(X * Y)/8 .. a byte is eight bits, binary. That only accounts for monochrome.. the total memory space on a 328 is just too small to keep the data map for the video.. and you'd need colorburst and all that stuff that Arduino won't make anywhere as easily as it makes "sorta" NTSC composite mono.
I'm picking up a 644 (40 pin Arduino-compatible AVR, more resources than a 328 but still a DIP).. if I remember right it has substantially more SRAM, so higher resolution data maps might be possible. The AVR core is plenty fast I'm betting, the 328 handles it awesomely.