I use an aggressive spam filter so very few spam-mails actually make it into my in-box, however, "good" emails can also end up in my spam box. This means I have to waste time browsing through the spam box at server level for legitimate emails or risk losing out on a potential new client.
When I repeatedly receive mail from the same spammer, I get mad, and sometimes I go after them. When a new spammer recently began bogging down my work email accounts I did a little sleuthing and found many complaints about this particular spammer on blogs and forums but no one seemed to know who the spammer really was.
I decided to cameo the company, using only information available to the general public that was obtained ethically (without deceit), legally, and for free as a case study on how to track down a spammer and file a complaint. As long as a spammer has an active email account or website, you can usually track them down. I do not recommend you waste a lot of time on tracking down spammer (unless "revenge" feels good) because they often shut down one shop and open up another before anything can really be done. Still, if you catch one, there are very stiff fines and penalties that can be imposed on companies who spam, scam, and "phish."
It is important that you never try and go head-to-head with any spammer. It is always better to contact their email provider, registrar, or hosting company. Spammers will not care about your complaints - but their server providers usually will take swift action to shut them down.