Regardless of their lack of remuneration, unpaid work is highly beneficial for anyone who wants to establish a valid and strong reputation in a field of work where there is competition to get in.
First, since you will not be paid, chances are that you will not have to adhere to a specific schedule. This means that you have the upper-hand in terms of being wanted and needed around especially if you do your job right. As you meet the people whom you are working with, you can establish a network of employees who will learn to trust you and respect the fact that you are volunteering. Whenever you are absent, chances are you will be missed more than if you were a regular employee because the fact that you are volunteering is what makes you stand out from the rest. That is a benefit as far as reputation.
Another benefit is getting the upper-hand in relationship to peers who hope to get in the field the traditional way: waiting to get called for a paid internship. If you make the move and get into an intership without pay, you will likely be given other incentives in lieu of money. Even if you do not recive any sort of incentive, the fact that you are unpaid may let you work your hours as it benefits you the most
Investigate whether the unpaid internship can transfer as college credit based on field experience. That may be perhaps one of the biggest perks because college is expensive and lengthy; an internship replaces a number of courses that may slow you down in getting ahead. Transferable experience is a sought-after resource nowadays.