Claude Monet on Artsy.net, including over 60 of his paintings plus additional information.
Claude Monet's Giverny, including images of many of his paintings, a biography on Monet, a list of museums with Monet paintings on display,information about Giverny and more
The Unknown Monet: Pastels and Drawings, an exhibit at the Sterling and Francine Clark Art Institute, Williamstown, MA, June 24 - September 16, 2007. I've been to this exhibit and thoroughly enjoyed it. I'd never seen any pastels by Monet nor any drawings, often preliminary sketches for oil paintings.
John Singer Sargent Virtual Gallery, including images of many of his paintings, books on him, an article on his painting method and more
34 works by Sargent at the Museum of Fine Arts, Boston.