The developers of the free Popup Maker plugin for WordPress are currently seeking beta testers for version 1.7 RC1.
Popup Maker 1.7 RC1
Their biggest update to date is focusing on improving existing functionality, reducing maintenance and the time it takes to implement new features in the future.
The new version comes with loads of interface changes. Instead of having many meta boxes in the popup editor, they have introduced a new clean single panel interface.
Also, they have included their extendable subscription forms in the free version. Please note that support for mail service providers is not provided in the free core plugin. However, they have now opened up their form API for third party developers. Submissions will be stored in a custom table for retroactive syncing to lists or export (not yet available).
WP Popup Maker
Trusted by more than 200,000 websites, the Popup Maker plugin can be downloaded for free via the WordPress Plugin Directory. It allows you to create virtually any popup you can think of. To enhance its basic features, it can be extended via a rich set of affordable extensions such as Exit Intent, Popup Analytics and Advanced Targeting Conditions.