Museums with excellent Italian Renaissance (1250-1600) collections searchable online:
UNITED KINGDOM
The British Museum, London
Major prints and drawings collection, coins and medals, decorative arts
Victoria and Albert Museum, London
Major sculpture and decorative arts collection
The National Gallery of Art, London
Major paintings collection
AUSTRIA
Kunsthistorisches Museum, Vienna
Paintings, armor, sculpture, decorative arts
FRANCE
Musée du Louvre, Paris
Major paintings collection
ITALY
Galleria degli Uffizi, Florence
Major paintings collection with remarkable range from Tuscany and other regions of Italy, prints and drawings
SPAIN
Museo del Prado, Madrid
Major paintings collection
USA
Metropolitan Museum of Art, New York
Major paintings collection, prints and drawings, furniture, and decorative arts
Heilbrunn Timeline of Art History
The Frick Collection, New York
Major paintings collection
The Pierpont Morgan Library, New York
Collection of drawings, books, and manuscripts
The National Gallery of Art, Washington, D.C.
Major collection of paintings, sculpture, prints and drawings
J. Paul Getty Museum, Los Angeles
Paintings, drawings, manuscripts, and decorative arts