Is there any way to get the current user inside a widget?

We are currently in the process of setting up a Customer Portal where our client's customers will be able to log in to view the bookings that have been made for them. We are currently saving the email address that will be used to invite them to the customer portal on the Account in CRM. This e-mail address is also being assigned to the bookings. Is there any way to get the e-mail address of the currently logged on user so that we can use it as part of the criteria in the record access?