A SharePoint Site Administrator can change passwords (but cannot view them). Here's how:
1. Login as Admin account.
2. Select "site settings" from menu.
3. Under "Manage My Information" section choose "View information about site users".
4. Click on the User that you wish to change passwords for.
5. Click on "change password", located near the bottom of entry.
6. Enter new password and confirmation then click "Okay".