Im not sure if this is an issue with Wordpress 3.0 and changes to function names but as far as I can tell this should remove the jscripts and css from the headers sitewide
add_action('wp_print_scripts','my_deregister_javascript', 100); function my_deregister_javascript(){
wp_deregister_script('ngg_script');
wp_deregister_script('thickbox');
}
add_action('wp_print_styles','my_deregister_styles', 100); function my_deregister_styles(){
wp_deregister_style('NextGEN');
wp_deregister_style('thickbox');
}