How to add a Subscription box? I would like to add a style-able Subscription box which will consist of a Heading, text field and a styled button in form of an image. Upon pressing the submit button I would like the user to be presented with some options in form of checkboxes as well as the option if they would like html or plain text email format.

How would I go about adding this to my drupal 7 site?
There are basicly two alternatives:


Using the Ctoosl Modal module. This module, included on the ctools project, is the most popular way to popup modal forms on Drupal, with lots of addon modules (like modal_forms). Here is a nice tutorial.
Using a custom module. You may find the following modules helpful: 


popup_message - which seems well supported. 
popup_announcement - this is a new module which seems closer to what you search for, with full html support, but with only a few downloads.  



With option 2, you should have to create the form and inject it into the popup using the forms API, so here is a form creation tutorial, and a stackexchange discussion about the best form creation method.