Remove posts from a certain category

plugin.php

<?php
/**
 * Plugin Name: Hide posts from category on home page
 */

add_action( 'pre_get_posts', 'my_pre_get_posts' );
function my_pre_get_posts( $query ) {
    // Category IDs to exclude
    $exclude_categories = array( 1, 2, 3 );
    if ( $query->is_home() )
        $query->set( 'category__not_in', $exclude_categories );
}

...and when people want to display a portion of their blog posts on their static home page, they can expand the $query->is_home() condition like this:

if ( $query->is_home() || $query->is_front_page() )
    ...

It seems that many WP developers use query_posts() which, in fact, causes more problems than it solves.

Sweet.