Two open-source tools can help on this way - both with simple usage and abolutely for free!
First SpamGourment - a really nice idea and practical for web-sides where you need an e-mail address to validate your registration (e.g.: a forum). By the help of SpamGourment you can create a temporary address to receive a specified number of mails, which are sent to your real e-mail address. All other mails are discarded and so no SPAM will receive you over this registration.
The second one to is to encrypt your e-mails to increase the costs reading them unwanted. GNUPG is the tool of my choice. You only have to create a public key and to exchange it with your communication partners to protect your privacy.
Never forget - many big brothers are watching you!!
