There is only one page in any blog that we can post to and by default it's the front page of the blog. Though we cannot post to more than one page we can create the appearance we have do so. What's critical is knowing that the static pages you have created will never automatically update. http://en.support.wordpress.com/pages/ Only dynamic categories Pages will automatically update.
Below is an example of a static page URL. Study it closely and note that no static Page can automatically update.
Below is an example of a category URL.
Study it closely please and note that only dynamic category pages can automatically update.
Setting up a menu is easy as pie, provided you know the differences between Posts and Pages, and the differences between static Pages, (which will never automatically update) and dynamic Categories pages which will automatically update when you publish Posts with Categories assigned to them.
The relevant support docs for creating custom menus, adding categories and sub-categories pages into it and ordering them to create drop downs are at:
Read this carefully http://wpbtips.wordpress.com/2010/06/30/posts-on-pages/
There are many common errors, misunderstandings and misconceptions when creating custom menus and there are some tweaks you can use to improve your custom menu as well.