I enjoy this plugin. It also has some great options in the settings.
http://wordpress.org/extend/plugins/alakhnors-post-thumb/
Upload/activate the plugin, then use <?php the_thumb(); ?> inside the loop to display the first image added to your posts/pages.
If you are using the_content in this loop, and inserted your first uploaded image within the post. You can use preg_replace as shown below to strip the img tags from the_content. This way to can display your thumbnails as above however you want and have text only in the_content. Replace your the_content line with below to do so.
<?php
ob_start();
the_content('Read the full post',true);
$postOutput = preg_replace('/<img[^>]+./','', ob_get_contents());
ob_end_clean();
echo $postOutput;
?>
Using both examples, you can do some nifty stuff for example float left on the thumbnail, to text wrap the post title, etc as well as the content.