Webmaster Tools
How do you get on Google's good side? Just ask Google! Google provides a web site called Google Webmaster Tools to help you get your site properly listed and indexed regularly. Google Webmaster Tools allow you to claim your site, upload a sitemap for your site, and see how the Google crawlers like your site. There is also a Google Webmaster Central blog and Google Webmaster Help if you need additional information.
Yahoo! doesn't offer tools like Google, but they do have a feature called Yahoo! Site Explorer, where you can claim your site and see how Yahoo! is indexing it, as well as the companion informational site, Yahoo! Search Blog for Site Explorer.
Search Engine Listings
While there are many search engines out on the market today, you really should just start with the some of the top databases: Google, Yahoo!, MSN, and DMOZ. Many of the smaller search engines will then pick up the listing from those. For example, Ask.com finds things on its own through links from sites it already crawls and AltaVista is powered by Yahoo!.
While you may get many, many e-mails from companies advertising that they will list your site with all search engines or give you some premium listing options, don't fall for this ploy! If you have additional time, after you've submitted to the top three, feel free to go back and submit to the FREE smaller search engines only. Just be aware of what you are signing up for!