How to add an extra field in a post and show it on the template

You can use a custom field eaisly then call into the template
(the image shows custom field <– my installation is in hebrew but would look the same and apears under the editor)

Then you can get the value of the field like so…

Inside the loop

<?php
$key="customField"; 
echo get_post_meta($post->ID, $key, true);
?>

Outside the loop

<?php
global $wp_query;
$postid = $wp_query->post->ID;

// mykey = field name

$key="customField";
$result = get_post_meta($postid, $key, true);
echo $result;
?>

.
Hope this helps… i would use custom post type but
this is the easy way to add a field to a post

Good Luck, Sagive.