Modifying the Width of Your Blogger Blog
Here is a quick step by step tutorial on how to change the width of your Blogger Blog. It will show you how to change the standard template so that the width is the same as this blog. This basically entails 4 things. First you increase the width of the Outer Wrapper and then you increase the width of the Header and then the two columns inside the outer wrapper. This would be the Post column and then the Sidebar column. Lastly you increase the width of your Footer.
Full tutorial here.