Google has launched a website where you can visit 17 of the great art museums of the world. Through googleartproject.com you can actually walk through these museums using Google's streev view technology. Each museum has selected one of its most prized pieces from its collection to be included in googles extremely high res view.
These images contain around 7 billion pixels, enabling the viewer to study details of the brushwork and patina beyond that possible with the naked eye.
Here's a detail from "The Birth of Venus"
You can zoom in much further even than this - it's quite amazing.
The tours of the museums allow you to navigate thru the museum using its own floor plan - is it just like being there?
And for a gallery/studio that's much closer to home you can check out the GilRoederStudio in Lincoln Massachusetts.