Chatelet, Gabrielle-Emilie, Marquise du: (1706-1749)  A noblewoman, who died young, following childbirth, she had translated Newton's Principia in to French. Also see http://www-groups.dcs.st-andrews.ac.uk/~history/Mathematicians/Chatelet.html.

P. Ehrenfest: Ehrenfest is one of the pioneers of modern theory of statistical mechanics and thermodynamics.  He classified the order of a phase transition.

J. Willard Gibbs: I have often asked my students in introductory physics courses if they knew the name of Gibbs. According to Maxwell, he was the greatest american scientist of the 19th century.  The answer has often been a blank stare.   When the movie "Amistad" had just come out, one adventurous soul offered if that was the linguist who translated the slaves.  Ahem, well that was Gibbs Sr.,  the father of the famous scientist.    Gibbs Jr. is also credited with the invention of vectors.

Here is another link: http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Gibbs.html

Warren Hastings: Warren Hastings was not a scientist, but a fascinating biography of him has been written by the noted physicist/author Jeremy Bernstein .  He was the first Governor General of the East India Company in India.  In the manner of Jefferson, Hastings organized expeditions to Bhutan and Tibet. He consolidated the British empire.  On his return to England, he was impeached (!) for maladministration.  In the trial in the House of Lords, Hastings was acquitted.

Thomas Midgley Jr.:  Here is someone who had the ill fortune to be hailed as a savior of humanity twice in his life and twice his contributions turned out to be something else.  I am often surprised how often people are not aware of him. He invented leaded-gasoline and freon.

Also see J. R. McNeill "Something New Under the Sun",  An environmental history of the twentieth-century world

Lewis F. Richardson:   Richardson invented, among other things, the field of meteorology and the law
of deadly numbers. The latter is the logarithm of the number of people killed in a conflict and is proportional to the frequency of its occurrence, somewhat like Richter's scale for earthquakes.

Benjamin Thompson: Benjamin Thompson was born in Massachusetts but being a royalist, left US for Britain after the war of Amertican Revolution.  He lived a life with high peaks of accomplishments, honors and riches followed by abyss' of failures, dejections and financial disasters.  Some have even called him a scoundrel of historical significance.  He is one of the founders of the subject of Thermodynamics.

Here is another link.  http://www.treasure-troves.com/bios/Rumford.html