Is there a way to display the popup only when the user clicks a button?

I would like my popup to display only when the user clicks on a button on the site.

This is what the guys over at LeadPages.net call a "2-Step Opt-In" and they say it has improved their conversions by up to 60%.

http://blog.leadpages.net/two-step-opt-in-process-list-building/

It's nothing more than a simple button, which displays a popup when you click the button.

I thought we might be able to do that with the Pop Up! plugin, no?