You would either have to have a list of emails from the users of your site or you would have to pay for it. Random bulk emails are not effective for marketing whitehat websites. If you found a newletter with a similar niche then that could be worth advertising in. If you want to send out email ads, google a service for it. The only way to send "bulk emain with a few clicks" would be if you site's software supported emailing the users (i.e. vBulletin).