I understand how to hardcode groups, archives, etc into theme however for among my projects i would need to hardcode some plug ins icons (especially subscribe2) and i am unsure how to get this done. I understand i'm able to add icons via icons menu in wordpress admin, but that is not what i am attempting to achieve, i am trying to put it together permamently in theme for later reuse. Any ideas how to get this done? Particularly with subscribe2?

You can include the widget through the normal means, and appearance the code on the website using View->Source.

Then, you have to edit the html template for that theme (based on in which you want the widget to look - primary entry, sidebar.html, etc) and add the code there directly.