I have been setting up a new site and was looking for a optin pop up that comes up alomg the bottom of the screen.
Came across this free plug in (I have no affiliation with this) and its easy to use and install.
Heres is an example of it working within minutes on a new site (Its still in development-work in progress)
Heres the URL for the wordpress plugin
If you know of any more plugins like this list em down for everybody.