A writer of memoirs, of fiction, of poetry and on science, Margaret Cavendish, Duchess of Newcastle, lived from 1623 to 1673. She now has a society celebrating her work, and is a frequent subject of academic study, with some describing her as an "early feminist".
She's eminently quotable, so bloggers are often borrowing her words.
They are also often transcribing her poetry, celebrating the fantastical worlds she created, examining her interest in science and involvement with the Royal Society, and reviewing books about her.