With Google groups , you can create and manage your own mailing lists, right from the comfort of your Google Apps  account. To get started, log into your Google Apps account and click on Groups at the top of your screen.
Google's Help Center should answer most of your questions. See http://www.groups.google.com/support/?ctx=ausers&hl=en 
Follow Google's instructions to create a group:
Once you've done that, we STRONGLY recommend you change some settings so you can control who can post, who can join, etc.
To change your group's access settings, click on the "Group settings" link on your group's homepage, then click on the "Access" tab . Carefully consider each item. Here's some advice:
Who can view?
- If you only want members to view messages, select Only members can view group content.
- Do you want this to show up in the Global Address List  in Google Apps? (This means any Humboldt user would see this address). if so, select List this group...
Who can join?
- If you want people to be able to join themselves, select Anyone from humboldt.edu can join.
- If you want to restrict it to only those you invite, select People have to be invited.
Allow External Members
- If you have (or will have) any people with email addresses that aren't @humboldt.edu, check this box.
Who can post messages?
- If you want to restrict to a small set of people, select Managers only (you'll have to make each of these posters a Manager.
- If all of your group members can post, select Members only.
- Want it more open? Select Anyone from humboldt.edu... or Anyone can post.
- Allow posting from the web means that your group members could reply to or add posts from Google groups, rather than sending an email (this can be handy).
Who can invite new members?
- This depends on your situation. Managers only? Or Managers AND members?
- Moderating can be a lot of work. If you want to do it, select All messages are held for moderation. If you don't, leave it as No moderation.