As much as it is important to have a good site(content, design) with clean valid links, it is also to have a sitemap that is UP-TO-DATE. Generally speaking when we talk about Sitemaps for a website, what comes to mind is a page, mostly static, where you’d have the sitemap laid out like a tree unfolding all the different parts of the website.
This usually is put on a single page so patrons may click through and find their way around easy. Much that this is a very good idea, an even better one is to let Google know you have a sitemap in XML format (here is mine) that links all ‘n sundry on your website. This helps Google crawl sites better and therefore rank the site better(be noticed).
I recently bought Google Sitemap automator that does a good job of grabbing your entire site and then create a sitemap.xml file. You can store the file locally or FTP it to the root of your site. You can do this for any number of sites. The only annoyance being it doesnt quite go past the firewall!
However, if you have just the one site and its running on WordPress, you might like to consider Arne Brachhold’s totally awesome Google sitemap Generator for WordPress. Absolutely brilliant and free! It also gives you the option to generate Sitemaps for folders outside your WordPress directory. But if you wanted to create an XML sitemap and didn’t want to buy a commercial product or use WordPress you could still get away by by using XML Sitemaps. Another brilliant tool. But if you wanted to use the utility as a stand alone application there is Unlimited Sitemap Generator very competitively priced. And dare I say you can even check broken links at a small cost to your paypal. Oh the choices these day. But this probably is a good thing.
So there, get crackin’ get your XML Sitemaps happening and notify google!

Thanks Amit, I’ve been meaning to get around to submitting a sitemap
You can notify Google and Yahoo! about your updated or new sitemap (XML) on Sitemap Writer’s homepage, just input sitemap’s URL.
Another good program is A1 Sitemap Generator
Scan large websites, span HTML sitemaps across multiple pages, calculate priority values for all pages based on internal linking structure etc.