Q: "How can I make my username always match my email address?"

A: An underrated, undocumented feature of Gmail is that it tolerates extra characters in your email address; take, for instance some arbitrary email address, datanerd@gmail.com. You could reach that same recipient by emailing any of the following addresses:

In a nutshell:

The awesome part of this feature is it enables easy searching of emails. Let's say you have an org you call "NewKillerApp". If you put +NewKillerApp in the username and email address you use for this org, you can later search on "+NewKillerApp" in your Gmail to find all the emails specifically related to that org.

Full details here: http://gmailblog.blogspot.com/2008/03/2-hidden-ways-to-get-more-from-your.html

Thanks to Dell's Luis Botero for reminding me of this cool feature!