This gives an example of how to query the wordpress.org plugins API for data on all plugins.

plugin_api.php

<?php
/*
 * Query the wordpress.org Plugins API
 */

$query = array(
    'action' => 'query_plugins',
    'request' => serialize(
            (object) array(
                'page' => 1,
                'per_page' => 100,
                'search' => '',
                'fields' => array(
                    'sections' => false,
                    'homepage' => true,
                    'tested' => true,
                    'last_updated' => true,
                    'description' => false,
                    'downloaded' => true,
                    'downloadlink' => true,
                    'tags' => true
                )
            )
    )
);

// Setup arguments for POST request.
$args = array(
    'method' => 'POST',
    'timeout' => 10,
    'redirection' => 5,
    'httpversion' => '1.1',
    'blocking' => true,
    'headers' => array(),
    'body' => $query,
    'cookies' => array(),
    'sslverify' => false,
);

$response = wp_remote_post( 'http://api.wordpress.org/plugins/info/1.0/', $args );

if ( ! is_wp_error( $response ) ) {

    echo '<pre>';
    print_r( unserialize( $response['body'] ) );
    echo '</pre>';
    
} else {

    echo '<pre>';
    print_r( $response );
    echo '</pre>';
    
}