How do I find people to email advertise to?

[Jake]

To recap Can-Spam regulations say you can't market to one with whom you have no established relationship.

Traditionally, internet marketers build their own list of subscribers, often using some incentive like a free ebook to get them to sign up to your list.
Constant Contact can provide the email submission for to put on a web site, some use paid advertising to get prospects to their "Squeeze page" designed solely to get people to sign up to your list.

Email remains an effective marketing method, allowing you to make multiple sales to a customer that you treat right.

There are email list owners who will mail on your behalf in a Solo Ad mailing.

There are also demographically targeted rental postal email lists derived from magazine subscriptions, product warranty cards, etc.
lists.nextmark.com has a large database of these mailing lists, they also have phone# and email lists, I can only guess the owner would email for you.