If you don't want to open the message, I'd recommend signing up to Spam Cop - and using a pre-scan system like MailWasher. Mailwasher enables me to see emails as they arrive, and read some of the content, without putting them into my inbox. Now that I'm also signed up to Spam Cop (I'm sure both of these facilities are findable on Google) I can tick the relevant box and the emails I know I don't want (Nigerian letters, phishing scams and the WoW alerts to a non-existent account) go off to Spam Cop, who can track the headers back and send notice to the ISPs.
Pretty efficient, even if it hasn't sorted out the root problem of the idiots who keep sending me the spam.