MacTutor History of Mathematics.
AWM Association for Women in Mathematics.

Here are some links to famous people mentioned in Sofya Kovalevskaya's letters.

F.M. Dostoevskii, author (access to a site in Russia listing Dostoevskii's works)
Charles Hermite mathematician
Sofia Kovalevskaia mathematician, author, political
Gosta Mittag-Leffler mathematician
Jules Henri Poincare mathematician
Alexander Pushkin author