Oh I remember reading a website all about the 2 finger V. It can mean sooo many things, from the equivalent of "flipping the bird" as knitandpearl said, to goodluck...
I know it more as the hippy sign for Peace, and also Goodluck, from Japanese cartoons, *it's realllly popular in Japan and has a couple different meanings there, the one I am familiar with is goodluck, as in you flash someone the Vsign to wish them goodluck...*
Wikipedia has a pretty extensive page on the Vsign
HERE