At first glance, you may wonder how smartphones and PDAs are related to spam. Well, there are a lot of services for these gadgets out there, and a lot of them require you to enter your e-mail when you sign up.

But before typing that key to your inbox, consider creating a dummy e-mail account. Free webmail will do. When you first sign up for a service, and it asks for your e-mail, just enter your dummy e-mail. Once it's clear the service doesn't spam you, you can simply use the service's options to change your address from your dummy to the real one. Do this for any service you're signing up for, no matter how legit they look; you never know.

You'll thus be able to do everything required by a service for joining, such as clicking on a link in a confirmation e-mail sent to you, without exposing yourself to services that dishonestly sell your online address to the highest bidder.