Here is the code I'm using:
<?php if (has_post_thumbnail( $post->ID ) ): ?> <?php $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'single-post-thumbnail', $size='thumbnail' ); ?>
I put the thumbnail size in the media section of the control panel and added <?php add_theme_support( 'post-thumbnails' ); ?> to function.php.
But the image is coming up full size instead of cropped to thumbnail proportions. Please let me know how to fix it. Cheers!