http://www.learner.org/interactives/renaissance/
This is an American website designed for students. It is an excellent introduction to the Renaissance.
http://www.ibiblio.org/wm/paint/glo/renaissance/
The WebMuseum‘s one-page article explores the changes that took place during the Renaissance, the period's major artists and thinkers, and the Renaissance’s impact.
http://www.learner.org/interactives/renaissance/symmetry_sub.html
Very good one page summary of the major changes introduced in Architecture, painting and music during the Renaissance.
http://www.bbc.co.uk/schools/gcsebitesize/history/shp/middleages/
This site gives you a lot of detail on medicine in the Renaissance. This is also an excellent revision site on the whole topic of the Renaissance.
Florence – the home of the Renaissance
http://www.channel4.com/history/microsites/H/history/i-m/medici.html
The Medici - A Chronology is a history of the famous banking family whose wealth helped to fund many artists.
http://www.pbs.org/empires/medici/
Very comprehensive site not just about the Medici - in fact everything you wanted to know about the Renaissance.
http://www.pbs.org/empires/medici/florence/pup/scape.html
From the above website take an interactive tour of the most important buildings in Renaissance Florence.
Leonardo da Vinci
http://www.pbs.org/empires/medici/renaissance/leonardo.html
User friendly biography of Leonardo da Vinci from the American educational website.
http://www.channel4.com/science/microsites/B/buildingthebest/
One-page biography of Leonardo da Vinci that is quite detailed.