Mary Lou Jepsen (via Pixel Qi - About Us)
For Ada Lovelace Day, I thought I'd highlight a currently active female technologist, rather than a Great Elder as many are doing.
Mary Lou Jepson is working on a technological problem near and dear to my heart: display technology in tablets and laptops. Good displays are expensive, ~$100 even for manufacturers. They draw too much power, and structurally limit everything about laptops, tablets, smartphones, and related devices.
Jepsen is already famous for running Intel's Display Division and founding OLPC with Negroponte, and their lovely dual-mode low power, green-as-it-gets screen(along with mesh networking and other interesting features).
Her new venture, the above-linked Pixel Qi, focuses entirely on screens. I hope she will do well.