Scientists Biographies for 5th and 6th Graders?

kimery asks: "My wife has just been named librarian for a 5th and 6th grade school. As part of the science program, students are required to read several science biographies over the course of the school year. The current biography collection consists mainly of dead (but oh so famous!) scientists. She'd like to expand the collection of science biographies, and would like to have your suggestions as to which scientists should be included. Bonus points for suggesting someone outside the 'usual suspects.' So, what scientists do you think would be interesting for a typical 5th/6th grade student?"