Who are some blind or otherwise disabled mathematicians who have made important contributions to mathematics?

Joseph Plateau should be mentioned. While Wikipedia classifies him as a physicist, this was back when there was much less distinction between physicist and mathematician. He more or less invented the "moving image", and was obsessed with light and the eye. He used to stare at the sun or other bright lights to try to understand the retinal fatigue experienced afterwards. Perhaps because of this, he went blind later in life.

With worsening vision, he went to other aspects of physics. The most interesting in my opinion is the semi-understood phenomenon now called "Plateau's Rotating Drop." If you suspend a viscous liquid in another liquid of the same density, and rotate the suspended drop at the right acceleration, then it will deform from a sphere to an ellipsoid to a torus. Here are some pictures from my old lab (my first research experience!) on this experiment.

It's said that he would rotate drops for hours, making his son describe exactly what was happening.

Plateau also worked a lot with capillary action and soap bubbles - a differential geometer before his time.

Louis Antoine was blind from age $29$ after being injured in World War I. After becoming blind, Lebesgue suggested that Antoine work on topology in two and three dimensions, partly because there hadn't been much research on such matters at that point and partly because, in Lebesgue's own words, "in such a study the eyes of the spirit and the habit of concentration will replace the lost vision."

Antoine did indeed pursue two- and three-dimensional topology and came up with what we now call Antoine's Necklace, which is an embedding of the Cantor set in $\mathbb{R}^3$ whose complement is not a simply connected set. This idea was later the inspiration for Alexander's Horned Sphere. Antoine was also an important influence upon Bernard Morin, another blind mathematician.

A. G. Vitushkin was also blind. Complex analyst at the Steklov institute. Best known for his work on analytic capacity.

For several others, see this paper from the Notices of the AMS.