I run a little business. I have no vacancies, but I could make some room for you to come in and learn how my business works. I can't afford to pay you, but you're welcome to sit around, shadow my staff, ask questions, and hopefully gain some valuable skills.
In return, I'd like you to respect my business, my staff, my customers and not be a drain on my resources - limited as they are in these tough times.
If you're able to demonstrate an ability to add value to my business in terms of reducing my costs or improving my revenue, there could be scope for hiring you into a paid position, after all, who doesn't want to grow? In any case you'll learn more than your school, college or university ever taught you.
Make it work for me, and I will make it work for you. If you have it in you to do what it takes, as long as it takes and as long as you understand that I don't owe you and you don't owe me, and that only you owe yourself, I'm desperate for the likes of you.
Use your initiative, learn about me, tell me what you can bring to the table. Let's talk.