Have a look at this plugin
http://wordpress.org/extend/plugins/wp-dummy-content/stats/
It is random content so if you need to always to load the same content you will have to look at the code and create your own version.
One pain of theme development is
setting up all the pages and blog
posts in order for you to see how your
site will look � one by one by one.No more!
WP-Dummy-Content is a WordPress plugin
that will generate a bunch of pages,
sub-pages and posts which you specify.
Titles and content are automatically
generated for you as well, and you
have a few choices as to the type and
length of content.One click generates an entire site.
Choose what type of content to insert:
single paragraph, multi paragraphs,
styled (lists, blockquotes, links,
etc.), or random. One click DELETES
all content created by the plugin!