Some not-so-obvious ways:

• A mailto: link. You can then subscribe (with double opt-in!) people that emailed to that address. The advantage of this approach is that the user doesn't have to write their email address. Great for mobile users. The downside is that not everybody might have an email client configured and it might be a bit confusing (although you can use mailto:[email protected]?body=instructions) to show instructions to the user in the email client (body is automatically shown in the compose message text)

• Facebook Connect or one of the many other social logins. They often provide you the user's email address too. Just make double sure the user is informed they are subscribing to an email list as it's not necessarily obvious this way.

My big fuckin annoying welcome mat that collects emails.paleoglutenfree.com/ Sucks i know but it works...

@stephenfjohnson you build that yourself or use a library?

@stephenfjohnson How well does this approach work as compared to other popup modals?