I’m trying out this photoshop plugin called Blow Up 3 by Alien Skin. [Check out the samples on their site — they’re actually not fooling you.]
It uses some interesting interpolation algorithms along with smearing and selective sharpening to retain sharp edges and try its best to avoid pixelation. In practice, it does a really good job at maintaining the original image even after enlarging by 200% scale. It’s not perfect, obviously since it’s trying to make up new pixel information that wasn’t there before. But it’s a marked improvement over the standard Photoshop bicubic method.
They market this toward photographers who want to crop and enlarge sections of photos, but it looks like this can be pretty handy for illustrators too, especially comic artists and those looking to print a smaller artwork at a larger size. I’ll take slightly smeary details over pixelated ones in a print.