Ahh, I was going to ask this same question, it's a fun effect that would be cool to add to Paint.net!
I think this is what Steve Hester had in mind:
http://www.axlrosen.net (click the AlexWarp link, needs JavaScript activated)
I remember using it years ago on a website when the guy let people use his Java applet, I still have the .class files if somebody can reverse engineer a plugin from Java to C# (if that's even possible)
Maybe you jest need to see what maths code is used or something (4 years of CSSE and I'm bloody potato at programming! )