Google (Webmaster central) and Yahoo (Site Explorer) have had webmaster tools for awhile. These tools allow you to see how the respective search engines see your site. Webmaster central will show you bad links (invalid or unreachable urls), and the last time your site was crawled. You can even see that last time your site map was fetched by Google's crawler. Site Explorer will allow you to submit the url of your RSS/ATOM feed so that Yahoo will "know" when you've published something new.

Later this year, Microsoft has announced that there will be a public beta of "Live Search Webmaster Portal," a collection of tools and information for site owners akin to the Google Webmaster Central and Yahoo Site Explorer offerings from those respective search engines. A private beta of these tools is about to begin.

Live Search Webmaster Portal: SEO Tools Coming From Microsoft

Microsoft is certainly playing catch-up here. I like Webmaster central the best so far. It will be interesting to see what tools Microsoft will offer.