Gmail already allows you to create multiple email aliases but there is one more thing that enables you to use @GoogleMail.com as your email address in addition to your actual @Gmail.com email address.
Yes, all Gmail accounts actually have two email address – one is @gmail.com and the other is @googlemail.com.
It means that if your email address is firstname.lastname@example.org then all emails sent to email@example.com will be delivered to firstname.lastname@example.org.
You can make use of this feature to reduce email spams and never miss any important email. Likewise Gmail is a popular email service so most of the spams are sent to @gmail address instead of @googlemail.com address.
For example: You may use @googlemail.com email address in your visiting cards, give it to your business friends and other important contacts etc while keep @gmail for online use such as on Facebook and your website etc.
Then set a Gmail filter to @googlemail.com and you will never miss out any important email from your close ones.