The recruitment channel in game (and the recruitment forum on Eve-O) will help you find any number of corps specialising in piracy, and several will "train" you. The TEARS alliance, the Tuskers and the Bastards corporations are particularly vocal pirate groups in the blogroll and they seem to have a lot of fun. (EDIT: The Black Rabbits are quickly becoming much more vocal in the blogroll, and they run their own pirate academy too.)

However, there are many forms of piracy. There is the classic bucklerswasher types, who track down targets and destroy ships/ransom pods, then there are the ninja salvagers who "collect salvage and keep systems clean" but also fuel their ships with the tears of rage of many miners and mission runners. There are also wardeccing groups who find easy high-sec targets and prey on them. I suppose some people could even call mercenary bands "pirates", and they would be almost correct from a certain point of view, but probably wouldn't live to brag about it. Which would suit you more is a decision only you could make.