One of the most effective ways of limiting the spam that you get is to use a “throwaway” email address for site registrations and product sign-ups. One easy way to do this is to sign up for an account with Hotmail, Yahoo! Mail, or Gmail and use that account only for the above type of transaction, and then use your normal email account for business use, regular correspondence, etc.

Another option is to use a brand new service called 10 Minute Mail. You can go to the site, get an address, use it to sign up for an account, check it to get the confirmation email, and then let it expire. Not only does this give you the benefit of using a separate email account to avoid spam, it has the added convenience of no password or username to remember. Click, copy, paste, done.