Watch the Simpsons Online with Free Episodes on Fox, this is completely legal unlike other alternatives.

Fox shows limited Commercials while showing the Simpsons Online. You can watch free episodes of the current season. Season 19 just has a few episodes. However, Fox lets you watch the simpsons online after every Sunday when they publish the new episodes for free. The stream could be of better quality, but who can complain when its online for free?
Simpsons new episode every Sunday this link.