There are many wonderful places to see and do in Iceland. Where to begin? I recommend that you visit and look over the posts on our blog: http://iceland24.blogspot.com/
There are some posts about places like the Westfjord, Snæfellsnes, Mývatn, Askja and other places which we thing are worth seeing. Of course you can´t do and see them all in just a week vacation. That´s why I recommend that you read carefully and plan with distance in mind.