Here comes my 100th Post.
You can submit your website and sitemap to Google, MSN and Yahoo. Now MSN is also supporting external sitemaps.
1. Google Webmaster Tools You need one Google Account for this
2. Yahoo Site Explorer You need a Yahoo account for this
3. MSN Webmaster Tools You need a Windows Live account (MSN Hotmail, MSN Messenger, or Passport account) to use this
Remember to use Robots in your site, since that will be an added advantage
Here is my Robots file content
you can even save it with a content
For the MSN, you can ping MSN with updates to your sitemap using their Ping URL Read it More from MSN Blog, MSN Support Cross-Domain Sitemaps
And if you are using Blogengine.net, you have a compatible sitemap (you van see my site map here http://yourwebsite/sitemap.axd, see mine sitemap). And for the ping service, Mads Kristensen wrote one extension for this. You can read and download the extension from his website here