Don’t buy or rent email lists, unless you know 110% that the company who offers such lists is kosher. If anyone offers you a list of 1 million emails for $99, or whatever price, run like crazy from them.
Same applies to joining online list services, such as YourLuckyList, The List Machine and ListDotCom. Although they promise you access to thousands of “subscribers” I have a feeling that those thousands of people are there for the same reason you are – to offer their stuff to you – so they won’t be so responsive to your offers. That’s just my experience, you’re free to give them a try – let me know how you do, please.
My philosophy behind email marketing is – relationships – and the only way to build a relationship is if you build your own list. But, you see, building your own list doesn’t necessarily mean you have to build it yourself, alone. You can team up with others, for example with someone who offers a service or product which is complimentary to yours, and do some kind of join venture with them.