We all know that two (or more) factor authentication makes for better security than just a user name and password alone. And many users have sensitive information that they send and/or receive via email, so making email accounts more secure makes sense. Google has announced that they are going to be offering two-factor authentication via their new “advanced sign-in” for Gmail, as they announced for Google Apps a while back. They call it “two step verification” and it requires you to enter your cell phone number and receive a code via SMS, or you can use a mobile app (available for Android, BB and iPhone) to generate the code. 
Some companies are now having employees use Gmail for their email, and even in organizations that have their own mail servers, many workers have Gmail accounts that they use as secondary mail accounts, so this is worth checking out. You can find out more in the Google Blog at
http://googleblog.blogspot.com/2011/02/advanced-sign-in-security-for-your.html