Product details page customization, specifically options drop down.

I just started playing with development mode. So it is possible that I have missed few things in documentation...

I am trying to customize how options are displayed on product details page. In my current template it is dropdown, I am trying to find code related to this, so that I can customize it. Can any one give me pointers if this doable and if yes where in code i should be looking at.

Thanks in advance.