Google recently updated Gmail to give all users the ability to delegate access to their email account (a feature that was already available for Google Apps users). This new feature can be accessed in the settings, under the accounts and import settings.
Delegates cannot change your account settings, passwords, or chat as you. “Each account will open in a different browser tab or window so you can view both accounts simultaneously, all while signed into your primary account. When you send a message from hikingfanfamily@gmail.com while signed in as hikingfan@gmail.com, it will appear as being sent by hikingfan@gmail.com on behalf of hikingfanfamily@gmail.com.” (via Google)
