Oh, the #1 top method that I have seen but not used (yet) is giving away something for free that is popular.
A client had a shampoo site that was built for them and they made a page that offered a free sample of their shampoo to anyone that would fill in a form. Then they forgot about it. Well I started to work with them 2-3 months later and I noticed that the email that the forms was being sent to was a POP3 mailbox that noone was checking. I told them about it and heard back that they had 10,000 emails!!!
They were really, really freaked out. They didn't know what to do about sending all those free samples with getting the samples made, packaging, addressing the packages, paying for the postage, etc.
They thought this was a huge problem, but when I talked to them, I told them they were looking at this the wrong way. Sure it's going to cost you some time and money, but look at the cost compared with other kinds of advertising where you get 10,000 people to give you their address and email...? If you can't send them all samples (because you ran out), you could contact them an offer them coupon with a nice discount.
I don't know what they did in the end, but they are still in business.