Welcome to the board, drmark.
Your demographic is irrelevant to spammers - they just have huge lists of e-mail addresses, and yours happens to be on their list. They don’t care if you’re old or young, male, female or Martian. Sending spam e-mails costs them next to nothing so they just splatter as many addresses as they can.
The common wisdom is to not attempt to unsubscribe, since this merely indicates to the spammer your e-mail address is real, and therefore makes your address all the more valuable to be used and sold to other spammers.
When you try to go to such a site and it leads to a non-existent page, that might mean that other people have complained about the spammer and his website has been shut down. Of course, it might be just that the spammer is a fly-by-night operation anyway, who packed his bags and left, as it were.
There is no overall “Internet police” since the Internet is a rather chaotic group of loosely-connected networks. However, with a bit of detective work you can trace down the spammer’s Internet Service Provider (ISP), and the ISP of his ISP also, known as the “upstream ISP”. Most ISPs have an “abuse” or “postmaster” account and most have an “acceptable use policy” that expressly prohibits spamming.
You should first first report the spammer to his own ISP, and if you get no joy there, to his ISP’s ISP, and so on. In order to do this you’ll need to view the full headers of the e-mail message (the way to do this varies depending on which e-mail software you’re using) and find the originating IP of the e-mail: remember almost all spammers fake the return and reply-to addresses in their e-mails. What an honorable bunch of people.
For more information - try www.spamcop.net. For tracking down IP addresses, www.samspade.org is pretty useful.
Unfortunately, even if you get a few spammers’ e-mail accounts and web sites nuked, there are plenty more out there and they spring up like weeds. Without some kind of tough legislation, it’s like trying to hold back the tide. ISPs vary in their attitude towards spammers: some are willing to take the spammer’s money and turn a blind eye, others will delete a spammer’s account (and even fine them) if there are just a few complaints.