Google Sitemaps is an experiment in web crawling wherein by you can using Sitemaps to inform and direct the Google crawlers, to speed up the discovery and addition of pages to the Google index.
Google Sitemap Generator plugin helps to generate a Google Sitemaps compliant sitemap of your WordPress blog. It is WordPress 2 compatible. It generates a static XML file in your blog directory and can also create a gzipped version of the sitemap. The sitemap includes your homepage, posts, static pages, categories and archive pages. The XML file gets automatically rebuilt if you change/edit/create/publish a post and can automatically tell Google about changes via Google-Ping. The user friendly interface lets you customize all parameters like change frequencies, priorities etc.
More details about the Google SiteMaps for Webmasters reveals
“A Sitemap provides an additional view into your site (just as your home page and HTML site map do). This program does not replace our normal methods of crawling the web. Google still searches and indexes your sites the same way it has done in the past whether or not you use this program. A Sitemap simply gives Google additional information that we may not otherwise discover. Sites are never penalized for using this service. This is a beta program, so we cannot make any predictions or guarantees about when or if your URLs will be crawled or added to our index.”
I found this plugin very useful to create a sitemap of my WordPress site in a few minutes, without any errors and ping google too. Now I am awaiting the Google crawlers…