explorer.muralarts.org/

This site is beautifully done and really shows how significant these murals are to Philadelphia. It expresses a unique cultural identity about the city.   It is playful, intuitive, dynamic, clean and easily navigated. Different individuals share their story's about taking the train, noticing the murals, and how it can changes thier thinking and additude. The art is in the streets, it is always open and for everyone. The exhibits speak for themselves.

Information is easily accessible on every mural listed.  It also shows images of the wall/building before it was painted and how the muralist went about painting it. 

This site inspires me, excites me, I spent hours on it! And I believe that is what makes a great museum website.  I am going back right now to look some more...