While I do tend to find pop-ups annoying, I am a fan of J.Crew's email address collection pop-ups. I've included two here: the green graphical one made it's first appearance about a year-and-a-half ago; the white one with imagery is a newer iteration, as of this past summer.

While some might question whether a pop-up would annoy more potential subscribers than it would acquire, my guess is, since they've continuted with it for almost two years now, it's been successful for J.Crew. In fact, you'll notice they've shifted from requesting only an email address to an address, a first name, a last name, a gender and a zip code, which suggests that folks were so forthcoming with their email addresses that "the crew" decided to try their hand at collecting even more useful data at sign-up.

Crew members, do tell! We'd love to benefit from your learnings.