Yahoo! is now offering an easy way to submit all your Web pages to their search engine. It's a simplified version of Google Sitemaps, by means of a text file that contains a list of your site's URLs.
In the past, you could only submit your home page to Yahoo!. With this new option
you can submit all your site's pages in a single submission.

Like Google Sitemaps and other search engine submission process, this "sitemap" does NOT guarantee that Yahoo! will crawl or index your pages, nor will it influence your keywords' rankings.

The Yahoo! "sitemap" concept is the same as Google's, aside from a simpler format and lack of reporting in its current version.

Steps to submit your site's URL to Yahoo! "Sitemap"
Step 1- Submit your home page to Yahoo! first. Before you do that, check to see if you are already indexed in Yahoo! or not.

Step 2 - Create the text sitemap file.
A text sitemap is simply a list of the URLs of your site in the form of a text file with the following format:
http://URL1...
http://URL2...
http://URL3...
Yahoo! request that the file be named URLLIST.txt. You can generate the list with any text editor. As with Google Sitemaps, there are applications that can help you automate the sitemap file creation. I personally use SiteMapBuilber.Net; it is a free application that creates Google and text file sitemap. You can get more information on the application and download at www.sitemapbuilder.net.

Step3 - Submit Your Yahoo! Sitemaps URL
To actually submit your sitemap to Yahoo!, you log into Yahoo!'s Free Submit page at http://submit.search.yahoo.com/free/request

Yahoo! will ask you to provide your Yahoo! ID and password. If you do not have a Yahoo! ID created yet, you can sign up on the same page and double check that your home is listed on Yahoo! because if you don't have a Yahoo! account ,that would mean you have not submitted your home page to Yahoo! yet.

Once you log on into the submission page, just enter the URL where the urllist.txt is located in your site (ex. http://www.yourdomain.com/urllist.txt) and select the Submit Feed button.

If Yahoo! times out when submitting your Sitemap, allow 24 hours and then return and try again. Do not resubmit your Yahoo! file immediately after the timeout, if that happens to you. I have the experience of having timeouts when submitting some of my sites.

Yahoo! sitemaps is following Google's footsteps on creating an easier way to telling Yahoo! about all your site's URLs in a single submission, saving a lot of submitting and spidering time.
There have been rumors that MSN is working on their own version of sitemaps. We'll be waiting.