Arts & Music
Renaissance Art 101 - from About.com.
Renaissance Art in Italy
Renaissance Art in Northern Europe and Spain
The Art of Renaissance Science - "Galileo and Perspective."  Art, architecture, astronomy and mathematics.
Renaissance Music Links
A Guide to Medieval and Renaissance Instruments
History of Ballet
Renaissance Dance Cheat Sheets

Castles
Castles of Great Britain - info on castles and castle building, life in a castle, castle defenses, medieval jobs, bathing and washing in the middle ages, medieval biographies, medieval women, medieval weapons and more.
Castles on the Web
Kids' Castle An interactive castle that allows you to visit all the different rooms and areas of the castle and tells about their uses.

Daily Life (Food, Clothing, Health, etc...)
La Couturiere Parisienne - Medieval and renaissance clothing.
Life in the Middle Ages Information on all aspects of daily life during the middle ages including feudal life in the castle, religion, homes clothing, health, the arts and entertainment, and town life.
Medieval/Renaissance Food Homepage
A Feast for the Eyes - Artwork from Medieval and Renaissance artist depicting food and feasts.

People
Renaissance Personalities
Renaissance Women

Knights and Clans
Knighthood, Chivalry and Tournaments Resource Library
Knights and Armor - from About.com.
Elizabethan Heraldry - see the colors and insignia worn by various houses and clans.
Historic Counterweight Trebuchet Illustrations - see how they waged war with these machines