Hold an interactive poll or survey on your web site. Ask your visitors to e-mail you their vote or opinion. You could send them a "thank you" e-mail and also mention a product you're selling. Tell them to subscribe to your e-zine so they can see the results of the poll.
2) Offer An Award
Ask your visitors to sign up for a chance to get a web site award. Have them e-mail you their contact and web site information. You can e-mail the web- master and tell him/her if they are the winner or not. Include your signature file at the end of your e-mail mentioning a product you sell.
3) Show A Prize
Hold a free contest or sweepstake at your web site. Ask them to give you their contact information to enter. Just get their permission to send them new product offers. You could also announce the winners to them, as well as sending new contest offers.