Use a throwaway email address for services which require an email address for registration but which you really don’t want to give your primary email address to. It’ll help keep your inbox spam free. Some providers include Inboxen, 10minutemail, Guerillamail, Mailinator, and Dispostable.
These services give you a valid email address which can receive subscription confirmation emails. If you use Inboxen, for example, you can tie each disposable email address you have used to the site you supplied it to. You can keep an eye on the emails that arrive in each addresses’ inbox, giving you a good idea which sites may be selling or passing on your contact details to third parties.