If you are looking into creating sitemaps for your website, here are some information to get you started:
- Sitemap file differences explained (by Microsys)
- Visual HTML web sitemaps (by TR Computing)
- Sitemaps Generator Blog (By Microsys)
- Google Webmaster Tools Blog (By Google)
Remember, creating sitemaps for your websites does not guarantee you get all pages indexed, but will most likely help get more indexed faster. If you have a website with lots of content, this can really help you get into long tail search queries 
