try this, most of people is using this - http://www.xml-sitemaps.com/ bu there is 500 URLs Limit in this
Yes, I use to generate sitemap using www.xml-sitemaps.com which is a good and free tools for websmasters.
You can get plugins for that. It must be installed in your website so that every time your contents are added site map generates automatically and updates your content.
xml-sitemaps.com is good site but here is another one you can give it a try..It can create unlimited number of pages and also supports subdomains. www(dot)web-site-map(dot)com
If you have a website that has over 500 pages then you must be doing a good business. Spend some cash and pay them and get them to create your sitemap for you.
ha ha, Thanks for that gem of advise, you are correct my sites are doing good business. But I also find it good business practice not to spend income on things I can get for free