Bullying is kind of in the eye of the beholder, so I've probably done things that counted as bullying to someone. I completely avoid the usual things like making fun of someone's appearance and stuff, but I'm certainly guilty of joining in online when someone has said something that made everyone gang up against them. Like the time I harrassed a zoophile for hours because he was in love with his cat. :P
`Twas brillig, and the slithy toves did gyre and gimble in the wabe;
All mimsy were the borogoves, and the mome raths outgrabe.