Twitter has Twitter Lead Gen Cards, which let you generate leads directly within a tweet without having to leave the site. A user's name, email address, and Twitter username are automatically pulled into the card, and all they have to do is click "Submit" to become a lead. (Hint for HubSpot users: You can connect Twitter Lead Gen Cards to your HubSpot Forms. Learn how to do that here).
Coupon: Unlike the job application, you probably know very little about someone who has stumbled upon one of your online coupons. But if they find the coupon valuable enough, they may be willing to provide their name and email address in exchange for it. Although it's not a lot of information, it's enough for a business to know that someone has interest in their company.