Generating an [tag-tec]xml sitemap[/tag-tec] that Google can use to find everything on your site is a staple of good, basic, no brainer [tag]SEO[/tag].
There are zillions of available plugins for WordPress and the [tag-tec]sitemap generators[/tag-tec] can be confusing to use if you don’t know what they do, how they do it, and how you can accomplish this slightly geeky task of getting your sitemap.xml done and up on your hosting account in the right place.
Chris Pearson, at Pearsonified.com, has done about the best job I have seen on taking you through this process.
Check out his post on creating a Google sitemap with the WordPress plugin that he recommends.
If your site is not completely and regularly spidered, you need to get a sitemap done for your site and keep it up month to month. Otherwise you are leaving rankings on the floor by not taking such a simple step in your overall marketing campaign.