A blog is a website and any WordPress blog can be restructured from being post based to being page base, but let's put that aside for the moment. Before you make any decisions at all read this comparison carefully please http://support.wordpress.com/com-vs-org/
You can use any theme here http://wordpress.com/themes/ to create a page based structure ie. a website rather than a post based structure ie. a blog. Before you make any decisions at all read this comparison carefully please http://support.wordpress.com/com-vs-org/
On one hand, none of the characteristic "blog" features like categories, tags, authors, dates, etc. can be removed from a free hosted WordPress.com blog, without purchasing an annually renewable custom design upgrade and doing the required CSS editing.
On the other hand, one can edit a WordPress.org theme free of charge. That's why I suggested you read the comparison > WordPress.com and WordPress.org: The Differences
If you remaining at WordPress.com suits you see > Using WordPress.com to Create a Website http://en.support.wordpress.com/using-wordpress-to-create-a-website/
Here’s a link to a custom menu walk-through > http://onecoolsitebloggingtips.com/2011/08/11/wordpress-com-custom-menu-walk-through/
There are many common errors, misunderstanding and misconceptions when creating custom menus and you can read about them here > http://wpbtips.wordpress.com/2011/12/19/custom-menus/