Can Admins login as a "general user"?

Can Admins login as a "general user"?

As an Admin, I sometimes forget that what I can see may be different than what other users can see. Also, when training, I would like to use an account that best reflects the interface that the students will be seeing (not my Admin interface). Is there a way that I can login as a typical user to see what they see? If I have to create a special user just for this purpose, it would be nice if I wasn't charged for this account, since it is not an account that would be "used".

Thanks.