LOVEFiLM

I've been subscribed to LOVEFiLM for a few months now and I think it's a decent service for the price you pay.  They seem to throw in special incentives to stay subscribed every now and again, which I also think is good.  For example, the other week I received an extra DVD from my rental list randomly, and yesterday I received three gift vouchers to give out to friends.  These vouchers give the user two months subscription for free, and each voucher was personalised with my name on, which was a neat touch.

Personalised voucher

Personalised voucher (inside)

Funny flyer

I think things like this do go a long way to keeping your customer base interested.