I would like to create a "blog-like" layout with a main story column on left that takes up about 2/3 of the screen and all my blocks on the right. Is there an easy way to do this?

Just put all of your blocks on the right. Then, in header.thtml in your theme folder, delete the reference to {left_blocks}

OK, and where do I change the width so that the centerblock (now left block) doesn't take up quite so much room?

You should do that in your style.css file using stylesheets. width: 67%; seems like it would do what you want.