I know my site isn't one of the biggest, but it's growing fast and its a PR3 site now, anyone can comment whether I should build a sitemap? Or what's the advantage of having one? http://www.chinamobilephones.net
It is better to have a sitemap regardless of whether your site is a big or small one. The advantage of having a sitemap is faster indexing by the google. The updated sitemap just reminds the googlebot to visit your updated contents and index new pages, if any. So always have one at hand and ensure your berth in google