Forum Moderators: Robert Charlton & goodroi
You can try making one with [xml-sitemaps.com...]
If your site is easy to navigate, there is no need. Google determines the importance and rank of a page by natural crawling. By simply giving it a sitemap, it loses the ability to determine where the link lies in the overall picture of your site.
That step is - make sure you server is configured to respond properly to the "If-modified-since" http request. The server should give a 304 status if there have been no changes to the url, and the server clock should be set accurately. This economizes googlebot's crawl budget for your site and allows more pages to be requested within any given budget.
The idea is that instead of requiring googlebot to fetch another full copy of an unchanged url, the server just replies with a few bytes - "no change".
You can also follow all the disciplines that limit canonical URL problems [webmasterworld.com]. Those steps also offer Google another kind of crawling economy.