You may be interested to buy those traffic blasting software in the market but please don't ever believe in buying a list. The fact that this kind of head count doesn't come to you directly and willingly will prove you still can't sell or please everybody in the list. Worse, you never know whether the people in the list have given consent to their addresses getting sold around, which is normally NOT the case.
The loyalty of your subscribers must be earned when it is a legal obligation to make it very easy for them to opt-out!
Buying expired or unavailable domains is a smart move. It's like people going to a shop when it has already closed down and they suddenly teleport (redirect page) to your shop. Once you bought it, make sure the web host company doesn't own it (YOU own it) and you can always transfer the domain to a cheaper host. Do a search for 'purchase expired domains' and you get good leads. I suggest WebExpired.com.
Buy domains with the right keywords related to your business. People going to an invalid hair gel site are not going to buy an e-book on viral marketing.
And of course, those cyber-squatters who make a living out of buying and selling domain names (read: GOOD keywords) are playing a different ball game altogether.