.Mac allows five email aliases per email account.

I don't know how long this has been available, but I just found out about it today. If you have a .Mac account, you have an xxx@mac.com email address. If you access that email account online, go to Preferences and set up an alias.

For example, if you use the Feedback button below, your email client will open with a blank message addressed to fightingtown at mac dot com (altered to avoid email harvest bots), with the title of this post as the Subject of the email. That's my first alias in my .Mac email account.