The PNG specification is nearly nine years old (it was made a W3C recommendation on November 10, 2003) and it has gained a lot of traction since that time. Back in 2003, I didn't like using the PNG format because it wasn't widely supported by web browsers. But now, it seems like PNG is the preferred graphic format for nearly everything. In fact, I tend to save most of my images in PNG these days unless there is some reason (quality and size being the primary ones) to use GIF or JPG instead. Did you know you can even create animated images in PNG?
Learn More: PNG
Screen shot by J Kyrnin courtesy Portable Network Graphics