Gmail: How to Allow Another Gmail User Account to Read, Delete, and Send Mail on Your Behalf

"You can now delegate email rights to another Gmail user. This can be useful if you want to give email access to your spouse or business associate and also give them access to your Contacts."

http://www.tech-recipes.com/rx/10217/gmail-how-to-allow-another-gmail-user-account-to-read-delete-and-send-mail-on-your-behalf