Incredible XML View Plugin 1.5 from Marc Liyanage
A little while ago, Marc Liyanage looked at the ClickToFlash and saw that it was straight ObjC, and with that, he embarked on writing an ObjC plugin for Safari that views XML in a manner similar to how IE shows it - formatted and stylized. The result is XML View Plugin 1.5.
The result is pretty darn amazing:
There's also an automatic updater, as well as the ability to modify the style with CSS and Javascript. Pretty impressive, I must say.
I don't use XML a lot, but when I do, it's really nice to have something that will format and display XML nicely.