WordPress uses the function wp_head() to add a bunch of code to the header of each page. Some of it is not absolutely necessary. This is especially true when using WordPress as a small business CMS, instead of a blog.
The code below removes the unnecessary code. Just add these to the end of your functions.php file.
This code applies to WordPress 3.0 and higher:
<?php
remove_action('wp_head', 'rsd_link');
remove_action('wp_head',...