load a template for a particular URL

frugal_budget.php

// http://wordpress.stackexchange.com/questions/9870/how-do-you-create-a-virtual-page-in-wordpress
add_action( 'init', 'frugal_add_rewrite_rule' );
function frugal_add_rewrite_rule()
{
    add_rewrite_rule( 'budget$', 'index.php?budget=1', 'top' );
}

add_filter( 'query_vars', 'frugal_query_vars' );
function frugal_query_vars( $query_vars )
{
    $query_vars[] = 'budget';
    return $query_vars;
}

add_action( 'parse_request', 'frugal_parse_request' );
function frugal_parse_request( &$wp )
{
    if ( array_key_exists( 'budget', $wp->query_vars ) ) {
        include 'budget-template.php';
        exit();
    }
    return;
}