Personally I prefer to charge something. The stuff I create is always worth at least something and I want subscribers to know that. Also a list built up of people who have at least paid something is always going to be more powerful even if it only cost them a $1. The fact is they will have crossed that barrier of using their credit card. This is the point that you lose most potential buyers or subscribers.
I would rather have a list built with ready made buyers than freebie seekers. That said building the relationship with either list is still going to be the most important part.
How do you build your list?