There is no such thing as "unsubscribing" from spam. All the spammer will do when you submit your request or even reply to the spam is confirm that your email address is a "live" one then sell it to other spammers, ensuring that you will receive even more spam.
In your case, about the only way to reduce the amount of spam you get is to go after the mailing lists that don't verify subscription requests. To do it the hard way, learn to read email headers and complain about each and every spam you get to the originating ISP and/or their upstream. An easier way is to simply forward these spam emails to your ISP (with full headers) and let them help clean up the mess.
At the time I ran Magic TOurnaments and Had A Website on which I posted the Results, also had one of those little Bulletin Boards, and also listed product to sell (before I went exclusively to e-bay) anyhow I had my e-mail address listed on the website. Most of the players would e-maill me prior to the tournaments to secure a slot it seemed to work fine (this was about 4 maybe 5 years ago BTW) but I had to change everything and shut down the B-board... the little freak would spam the board with some fairly disgusting language and suggestions as well.
BTW I am not with that ISP any longer and the little butthole ended up getting busted some drug stuff and actually served some time (wow there is a shocker) of course now he is getting some kind of college courses provided by the government... doesn't it feel good to know your tax dollars are going to such a worthy cause... :-p