A short listing of some of my favorite masters and samples of their work.
Many have asked for such so I'm providing this short listing of some of my favorite artists and their pictures.  The list is presented in close to chronological order.  I've not included all my favorite artists by any means.  Some of the most recent have limited representation on the web due to copyrights still in effect.  
Here you will find no current photographic 'print' artists of the popular genre.
All links will bring up a new browser window - one cannot hijack another's work and present it as a part of his own.
Favorite Art Website _The Web Museum  
This site has an artist index to surf at leisure.
If you're feeling a bit devilish then try Heironimos Bosch.
The Oldest Favorites - the caves.  Go spelunking into prehistory.
Chauvet Pont du' Arc Modern DNA analysis indicates that some 5,000 humans migrated out of Africa about 50,000 years ago.  In 1995 a cave was discovered in the south of France.  In it were the oldest paintings yet discovered at 35,000 years ago.  The master(s) who made those works equal any that I've seen in museums across the country.  Everything I learned in art school is pretty much found at Chauvet Pont du' Arc.  This just 15,000 years after humankind migrated out of Africa to populate all of Europe, Asia, and the Western Hemisphere.  How long humans had been painting images of things on perishable supports or just made scratches in the earth will always be the great mystery.
http://www.culture.gouv.fr/culture/arcnat/chauvet/en/
Lascaux Another French Paleolithic cave with marvelous horses.
http://www.culture.gouv.fr/culture/arcnat/lascaux/en/
Altimira A Paleolithic cave in the Spanish Pyrenees with awesome bison.
Pablo Picasso, THE master of the 20th century, was taken there.  Upon leaving the cave he was asked for his comment.  He summarized his spelunking adventure by saying, "We have invented nothing - it's all in there."  At the time Pablo had already created non-representational art and given it credibility and had reached world renown. 
http://www.showcaves.com/english/es/showcaves/Altamira.html
American Favorites
Thomas Eakins _Eakins' Life Summary
Edward Hopper _Hopper's Life Summary
Jackson Pollock _Pollock's Life Summary
_Pollock's -.Shimmering Haze
European Favorites
Pieter Brueghel, the elder _Brueghel's Life Summary
_Brueghel's The Fall of Icarus - (Spring)
_Brueghel's The Hunters in the Snow - (Winter)
Quite possibly this is the first realistic snow scene in Western European art.
_Brueghel's The Harvesters - (Summer)
Rembrandt van Riin _Rembrandt's Life Summary
_Rembrandt's Aristotle Contemplating a Bust of Homer
_Rembrandt's The Hundred Guilder Print
_Rembrandt's Belshazzar 
Pieter Paul Rubens _Rubens' Life Summary  Artist, statesman, knighted by England and Spain for diplomacy
_Rubens' Peasant Dance  Louvre version.
_Rubens' Peasant Dance Berlin version documented to have been painted in a single day.
Antoine Watteau _Watteau's Life Summary
_Watteau's Embarkation from the Isle of Cythera
_Watteau's other version of 'The Isle of Cythera
_Watteau's Drawing of a Little Girl  A drawing in black, red and white chalk by a master.
Jacob van Ruisdael _Ruisdael's Jewish Cemetery   He had the audacity to paint outdoors.
The first stone on the path to Impressionism.
Meinhert Hobbema _Hobbema's Life Summary  Ruisdael's only know pupil. 
The second stone on the path to Impressionism.
Thomas Gainsborough _Gainsborough's Life Summary
_Gainsborough's Hunting picture of Mr. Andrews and his wife
The third stone on the path to Impressionism.
John Constable _Constable's Life Summary   An English country boy who loved Dedham Vale and the Stour region.  It's now known as Constable Country.
He  sent his painting of Willie Lot's house, The Hay Wain, to an exhibition in Paris due to a lack of recognition in England.  
The fourth stone on the path to Impressionism.
Eugene Delacroix _Delacroix's Life Summary  He defined the Romantic style in 19th century French painting.  Ingres defined the opposing Classical style.
_Delacroix's Massacre at Chios
Delacroix saw Constable's The Hay Wain in Paris and repainted portions of this painting after returning to his studio.
The fifth stone on the path to Impressionism.
Fransouis Millet _Millet's Life Summary  He had a broad influence on the impressionist group and especially so on van Gogh.  He is the beginning of the Barbizon school.
_Millet's Walk to Work  He began depicting scenes of everyday life.
Andre Daumier _Daumier's Life Summary  Quintessential social realist
_Daumier's The Third Class Carriage
Camille Pissarro _Pissarro's Life Summary  Impressionism begins with him.
The only French Impressionist born in the western hemisphere.
He is the teacher to all the impressionist group and the glue that bound them.
_Pissarro's Peasant Girl with a Stick
_Pissarro's Le Pont-neuf
Claude Monet _Monet's Life Summary  He was discovered doing political caricatures for tourists at a beach and told to go study in Paris.  All that needs to be said of him was said by Paul Cezanne, so-called the father of modern art, "They say that Monet is only an eye but my God what an eye."
Vincent van Gogh _Vincent's Life Summary
He took some measure in my own getting used to and understanding him.
Coming to Paris in 1886 under the tutelage of Pissarro he found his art and changed the course of Western European art before he left this world just four years later in 1890.  No meteor ever burned so brightly.
Please don't denigrate him to me unless you've done anything remotely equal.
_van Gogh  One of innumerable self portraits.
_van Gogh's Portrait of the Postman Roulin
_van Gogh's Wheat Field
_van Gogh's Green Wheat Field
_van Gogh's .Orchard with Plum Trees
_van Gogh's Starry Night  All the swirling light objects in the sky are celestial bodies.as confirmed by astronomy.