Google Sites have now introduced Google Webmaster Tools support.  Not only has Google Sites provided somewhere to paste the your verification meta tag but they're providing an automatically generated sitemap!

Google Sites have provided help pages for the Google Webmaster Tools setup, but I've found they have not given an example of how to use the Google Webmaster Tools with a site that is using a web address mapping, so I include one below, using this domain as an example.

Using Google Webmaster Tools with Google Sites' Web Address Mapping

This site's Google Sites address is http://sites.google.com/a/steegle.com/steegle and I use a web address mapping of "www" so you can find this site at http://www.steegle.com/.  To use the Google Webmaster Tools with www.steegle.com here's what you need to do:

Verify a Google Site with a Web Address Mapping

1. Sign in to the Google Webmaster Tools (this can be any Google Account, and does not have to be the one you use for your site);
2. Use the Add Site button and type the URL of the site you want to add - www.steegle.com for example - in the Enter the URL of a site you'd like to manage box and use the Continue button;
3. Make sure the Verification method drop-down box is set to Meta tag and copy the meta tag given;
4. Open a new browser tab or window, and paste in the Google Webmaster Tools verification box on the General tab of the Manage Site page of your site (e.g. http://sites.google.com/a/steegle.com/steegle/system/app/pages/admin/settings - but use your domain and site), and use the Save Changes button;
5. Return to the Google Webmaster Tools and use the Verify button and you should have verified your site.

Submit a Sitemap of a Google Site with a Web Address Mapping

1. Sign in to the Google Webmaster Tools (if you haven't done so already);
2. Choose the site you want to upload a sitemap for and use the Submit a sitemap link under the Sitemaps column follow the Add link for the site you wish to add the sitemap for;
3. Use the Submit a Sitemap button and n the box next to your site URL enter system/feeds/sitemap and then use the Submit Sitemap (on the right) to add it to the list of sitemaps.
4. Come back later (hours or days) to see the pages the Google Webmaster Tools has found from the sitemap.

Further Search Engine Optimization (SEO)