This is a gem. There are actually number of ways to get multiple gmail addresses, here are few examples:

abc@gmail.com is also same as abc@googlemail.com. Awesome feature, isn’t it?
Embed random text to your email ID using ‘+’ sign,  like: my+mail@gmail.com

Gmail Manager – manage multiple Gmail accounts, receive new mail notifications, view unread messages right from your browser statusbar. “…The Gmail Manager Firefox add-on obviates the need to keep your Gmail open in a tab all the time by displaying your email info in a statusbar pop-up…” [via LifeHacker

Gmail Signature Float – moves your mail signature to the top of the message rather than the bottom