All websites should have a Webmaster Tools account set up for it. Inside this app is where you submit and can review the status of the submission and indexing results. It's also FREE. Also check out our Sitemap Ping Services - Sitemaps AutoDiscovery Allows URL Submission To Search Engines This will show you how to Ping Submit your sitemap to Google, Yahoo, Bing and ASK. Just do it ONE time after you update the XML Sitemap.
Google Webmaster tool is brilliant tool that can help you check for various things regarding your website. You should join it for the sitemap query also.