She's often considered the first computer programmer but obviously not in a literal sense--when she translated Charles Babbage's notes (about the Analytical Engine?) she added a lot of stuff herself and it included an algorithm meant to run on the engine, so even though that machine was never made, it was a sort of program. What I find more interesting about her notes is how she had the idea that computers could be used for something besides just computation, when no one was thinking about these machines that way.
Her whole life story is really interesting, because she's the poet Lord Byron's daughter, and her mother didn't want her to be crazy like he apparently was, so she had Ada learn logical stuff like math.
(I'm obviously a fan of her. I even have a necklace that says "curious" in her handwriting.)