Last Updated Jan 4, 2011 11:48 PM EST
It's quite simple to do. You can give anyone with a Gmail account permission to manage your Gmail inbox with just a few clicks. To do that, click Settings and then click the Accounts and Import tab. Near the bottom, you should see a new entry labeled Grant access to your account. Enter a valid Gmail address.
When your assistant verifies the request, they'll be able to view their own Gmail and yours in separate browser tabs. And while your assistant can send and receive e-mail on your behalf, you still have full access to your messages and only you can change your e-mail settings. For a few more juicy details, check out the Gmail Blog.