Here are the top search engines you submit your site for free.

Google: http://www.google.com/addurl/?continue=/addurlWindowsLive/MSN: http://search.msn.com/docs/submit.aspx

Open Directory Project: http://www.dmoz.org/add.html

Librarian’s Internet Index: http://lii.org/cs/lii/create/todo

Yahoo Search: https://siteexplorer.search.yahoo.com/submit

Alexa: http://www.alexa.com/site/help/webmasters

While looking for information on how to submit sitemap to MSN, I can across this piece of information from Yahoo blog. To add sitemap to robots.txt, just add the following line:

Sitemap: http://www.example.com/sitemap.xml

In case you have multiple Sitemaps, you can point to your sitemap index
Sitemap: http://www.example.com/sitemapindex.xml

To do this, simply add the following line to your robots.txt file:

Sitemap: http://www.example.com/sitemap.xml

Please provide the complete URL for your Sitemap on this line. We will pick it up wherever you put it in your robots.txt file. This directive is not specific to user-agent. If you have multiple Sitemaps, you can point to your Sitemap index file on this line.

It is good to know that one does need to manually submit site map to Google, Yahoo and MSN. I hope this is going to be the standard very soon.