The original Renaissance man, Leonardo da Vinci was not just a painter, but also an inventor, military engineer, sculptor, illustrator, architect, and scientist. His talents were extraordinary, yet he left many paintings unfinished, and never published his journals. [Editor's Note: An updated version of this topic can be found here: Leonardo da Vinci]
This comprehensive site for fourth- through eighth-graders, created by the Boston Museum of Science, brings Leonardo's work alive through activities. It is divided into four sections: Inventor's Workshop (Leonardo's machines), Leonardo's Perspective (Renaissance drawing techniques), What, Where, When? (a brief bio), and Right to Left (his curious habit of writing in reverse). The online activities include three Shockwave lessons in perspective and the opportunity to decipher one of Leonardo's inventions. Is it a drill, a crane, a wrecking ball? Teachers and home schoolers should read the Introductory Letter for a complete lesson plan.
You'll find it all here, including Leonardo's most famous paintings: the Mona Lisa and the Last Supper. Much has been written about the Mona Lisa and the source of her enigmatic expression, which seems both alluring and aloof. Leonardo himself loved the portrait, and carried it with him until it was eventually sold to FranÃ§ois I. Very little is said about the Last Supper, except that Leonardo's fresco preparations were so poor that the painting is almost disappearing. In general, I found the commentary uneven, but the WebMuseum does present a large gallery of sketches and paintings.