I enjoy Dali the best. His far out paintings have always inspired me and the colors, WOW!
http://www.salvadordalimuseum.org/
I also enjoy Van gogh quite allot also.
http://www.vangoghmuseum.nl/
The real master though is Da vinci overall for his works blow me away as well as his sculptures, inventions and frescos.
http://www.mos.org/leonardo/