Google has introduced a new service,
Google Sitemaps, for website publishers or webmasters to inform Google about their sites. The service, which is still in BETA, will help Google search engine to crawl pages that are hardly accessible thru links. If you do not know about this, all pages of your site are actually crawled and cached by a search engine "spider" through links in your site.
To use this service, you will have to create a sitemap in XML format. You can create it with a
sitemap generator (runs on Python), or possibly write a text file with URLs on your own. After you have created the sitemap (an XML file), you will need to upload the file to your site before you can submit its link to Google thru
this page. They also accept syndication feeds such as RSS and Atom. A more comprehensive guide is made available by Google at
this location.
In addition to that, there's a sitemap services for mobile devices. Read more about it
here.