Following up on my "15 Suggestions for Marketing your iPhone Application" post, Shane Crawford of Blue Lightning Labs told me that the latest version of his application Mathemagics was just approved for the App store, with in-app email list signups.
I grabbed some screenshots of the Settings window (visible by clicking the "i' button in the lower right corner of the main window) of the process, in case you want to implement something similar. Note that he is also providing a way to follow @bluelightnin on Twitter by prompting you for your twitter information and performing the follow directly.
Congratulations Shane, and thanks for sharing the news.