I use mail aliases to stop spam. For example if you go to
CJB.NET and signup for a free url redirection you also get free email aliases. Just signup using a fake url or something you would use like
www.techguy.org and then turn on Mail Forwarding so that
anyalias@yourdomain.cjb.net will be forwarded to your real e-mail address. Then when you signup for a service on a website you can use a made up address but with an @yourdomain.cjb.net this will ensure that you still recieve confirmation codes and passwords. If you recieve spam from the site you can simply go to the mail alias section of your acount options and create an alias for the address the mail comes from. That means any spam they send you will be bounced back to them and they will have to remove your address from their datebase. You can also use it if you want to give out your address on forums such as this one for people to send you files or just e-mail you without them getting your real address!