Creating group contact lists through Google is a great way to manage and organize how you send and share information. Below is a tutorial video on creating contact groups in Google. Why is this helpful? Let's say you want to e-mail all the students in your 4th hour class or all of the teachers in a committee group. You can great a Google Group for "4th Hour" or "DEA Members" and then you can instantly send emails or share documents with this one group instead of having to type in all of their emails.
If you already have a list of contacts in your Address Book application, you can export all those contacts to Gmail.