Google Adwords As a List Building Tool
Here is a quick tip for you. I have been using Google Adwords to generate subscribers to lists. If you are targeting a specific market you can build a special landing page and campaign that will take the users to a page to subscribe to your mail list, newsletter,request info page, free bonus, etc.(anything where you want to build a contact list)
I have seen anywhere from 20-85% sign up rate for this tactic. It is very targeted, and I usually use this if I have an idea of what the lifetime value of the average subscriber is.
This can be used to build a subscriber list before you launch a specific product or service. It can also be used simply as a lead generation sales tool.