The professionals all agree that your mailing list is your goldmine. Your goal as a serious marketer, is to build your own email mailing list that you can market to - with their permission, of course. These great free programs offer email capture, lead processing and autoresponder message control. Although they usually have ads in the messages.
Bravenet
GetResponse
FreeAutobot
Of course, you may be lucky enough to get autoresponders included with your hosting. My hosting account with Kiosk provides an unlimited number of autoresponders with your paid hosting. I have several autoresponders with them, for separate programs. One for my main mailing list, to send t my newsletter, others when information is requested on a specific program. From experience, information should be sent at intervals. It is supposed to take an average of 7 messages to convince someone to buy something.
Capturing people's email address is the most important thing you can do. Even the best websites may only get about small signup/conversion rate from their visitors. But following them up via email can increase that rate. So capture their address, by offering them something free, and then follow them up with one of the autoresponders mentioned above, to remind them how good you are, and how much you are willing to help them.
This is where people talk about front-end and back-end. People may join your list as they buy your main front-end product, or to get a free ebook or course. Then you can periodically continue to offer them related products later on, that they may be interested in, as back-end products for satisfied customers.
You can buy lists of names of people who are willing to join your list. Allow them to opt-out at any time. Make sure you buy from a reputable company, to avoid getting spam complaints. Get personal references from people who have used the company.
A common way is to write a series of lessons about a particular topic, with a catchy title, such as "Seven secrets to Marketing Success". Save them in an autoresponder. Advertise your lessons. People have to enter their email address to subscribe to your course. Particularly if you offer something for free. And then they are usually too lazy to unsubscribe.
But you have to provide value to your list. If you are constantly mailing them ads, soliciting their money, without giving anything back, then they will get sick of the junk mail, and unsubscribe. I know I do.