Great Email marketing tip I learnt from Mark Ling of Affilorama.com fame known as the Day 7 Trick.
Send an email to your list on the 7th day .
Create a Free report. Tell your list that you are going to sell this product/report for $ 47 or so. Tell them to buy a product and send you the receipt and then you will mail them back the FREE report.
You can either make the Free report yourself or outsource it to somebody via Elance.com or any other site your may prefer.