It's important to track your site's SEO performance so that you can see if your efforts are paying off. Make use of the many free analysis tools out there, including:
Yahoo! Site Explorer — Lets you find out detailed search-engine-related info on each page of your site, including the most popular pages and the inbound links to each page.
Google Webmaster Tools — Gives you all sorts of details about how Google sees your site, such as problems crawling your pages and suggestions for how to improve your HTML.
Google Analytics — Reports on vital traffic data such as visitors, pageviews, traffic sources, keywords, and lots more. Also lets you set up goals so you can see how well your SEO campaigns are performing.