What an amazing resource from LearnOutLoud.com, gratis:

LearnOutLoud's Art Masterpieces is a collection of essays on some of the most important works of art ever created. These carefully selected writings provide exciting commentary on the work of such masters as Leonardo Da Vinci, Raphael, Michaelangelo, Titian, Sandro Botticelli, Rembrandt and many more. If you've ever wanted to gain a deeper appreciation of the great works of Western painting, then this audio series will be an invaluable compliment to your exploration.

Twenty-two paintings are covered in this collection and each MP3 file covers a different painting and has a high quality image of the art work embedded into it (which can be viewed in iTunes). Also included in this collection is a supplemental PDF which features images of all 22 paintings.

Paintings covered in this collection are:

The Birth of Venus
Painted by Sandro Botticelli in 1486
From "The Renaissance" by Walter Pater

The Dream of St. Ursula
Painted by Vittore Carpaccio in 1495
From "Fors Clavigera" by John Ruskin

The Last Supper
Painted by Leonardo da Vinci from 1495-1498
From "Werke" by Johann Wolfgang von Goethe

The Creation of Adam
Painted by Michelangelo in 1499
From "Michelangelo" by Estelle M. Hurll

Mona Lisa
Painted by Leonardo da Vinci between 1503–1507
From "The Renaissance" by Walter Pater

Pastoral Concert
Painted by Giorgione in 1508
From "One Hundred Masterpieces of Painting" by John La Farge

The Ecstasy of St. Cecilia
Painted by Raphael in 1514
From "Letters From Italy" by Percy Bysshe Shelley

The Assumption of the Virgin
Painted by Titian from 1516-1518
From "Voyage in Italy" by Théophile Gautier

The Transfiguration
Painted by Raphael between 1516-1520
From "Raphael" by Estelle M. Hurll

The Mystical Marriage of St. Catherine
Painted by Antonio da Correggio in 1520
From "One Hundred Masterpieces of Painting" by John La Farge

Bacchus and Ariadne
Painted by Titian from 1520–1523
From "On the Productions of Modern Art" by Charles Lamb

The Last Judgment
Painted by Michelangelo from 1535-1541
From "Trois maitres" by Alexandre Dumas

The Descent from the Cross
Painted by Peter Paul Rubens between 1612-1614
From "Les Maîtres D'autrefois" by Eugène Fromentin

Charles I
Painted by Anthony van Dyck in 1635
From "One Hundred Masterpieces of Painting" by John La Farge

The Shepherds of Arcadia
Painted by Nicolas Poussin between 1637-1638
From "One Hundred Masterpieces of Painting" by John La Farge

The Night Watch
Painted by Rembrandt van Rijn between 1640-1642
From "Maîtres d'Autrefois" by Eugène Fromentin

The Maids of Honour
Painted by Diego Velázquez in 1656
From "One Hundred Masterpieces of Painting" by John La Farge

Embarkation for Cythera
Painted by Jean-Antoine Watteau in 1717
From "L'Art du Dix-huitième Siècle" by Edmond and Jules De Goncourt

Oath of the Horatii
Painted by Jacques-Louis David in 1784
Compared With:
Dante and Virgil
Painted by Eugène Delacroix in 1822
From "How to Study Pictures by Means of a Series of Comparisons of Paintings and Painters" by Charles Henry Caffin

The Entry of the Crusaders into Constantinople
Painted by Eugène Delacroix in 1840
From "One Hundred Masterpieces of Painting" by John La Farge

The Gleaners
Painted by Jean-François Millet in 1857
From "Jean Francois Millet" by Estelle M. Hurll