Oddly enough if you get the type of spam that has the click through "remove me from your spam list" at the bottom and you do, you actually get removed (not like in the old days when this action was considered verboten as it just confirmed you email address). Other than that, downloading a program like mailwasher might ease you burden somewhat. It can be found at www.download.com
Also it is a good idea to have a disposible account like hotmail or yahoo which you can use to sign up for stuff.