Creating a sitemap for a new site is not that hard. But as you add more pages, the process becomes a whole lot more time consuming. Companion Sitemap Generator is a handy plugin that creates a sitemap of your site that updates every hour. You can have posts, pages, post categories, tags, and custom post types in your sitemap.
Companion Sitemap Generator comes with a robots.txt editor, so you can set rules for crawlers visiting your site. You can change update frequency from the back-end. Want to exclude certain pages from your sitemap? No problem.