There are many Popup email subscription widgets for blogger out there published by many blogs including BTNT, You can check the previously published Popup subscription widget on BTNT below.
- How To Add Pop Up Email Subscription Form For Blogger Using Jquery
- How To Add One Time Popup Email Subscription Widget For Blogger
Also, It comes with a simple eye catching flat design. Click on the live demo link to have a look at the demo yourself ;)