Just a quick and dirty code snippet which basically allows you to display the total number of posts which have been published on your blog:
<?php $numpost = $wpdb->get_var("SELECT COUNT(*) FROM $wpdb->posts WHERE post_status = 'publish'"); echo $numpost; ?>
There's nothing pretty about it - it'll need some spicing up but I'm sure you'll be able to sort something out with a little CSS. I would also like to point out that this code snippet does not include any draft posts when calculating the total number of posts - only the total number of published posts.