Albert Einstein (1879-1955) was certainly the most famous scientist in history, and indeed, judging by the continued public interest in him, is one of the best known figures of human history. This coming year (2015) marks the centenary of his greatest achievement - the General Theory of Relativity.
Einstein was a complex and multi-faceted personality, and in some of the links here you can find out more about this. These links contain both a short summary and a somewhat longer summary of his life, and also more lengthy discussions of both his philosophy and general beliefs - all of these should be accessible to non-scientists. There are also introductions to some of his scientific work. These are written for the 'educated layperson', ie., there is very little mathematics.