Many times when you sign up for something online, like membership to a site or for a free promotional offer or something similar, you are asked to provide an email address. Now, you don't have to use your own email address and subject yourself to possible spam in your email account.

You can use what is called a diposable email address to sign up for things online.

The below link goes to an article that lists the top 20 sites that provide you with a disposable email account.