There are literally MILLIONS of search engines out on the web and it would be impossible to get decent ranking on any number of them. Thankfully however, you don't need to worry about the majority. The search market is dominated by three main players, google, yahoo!, and live (formerly MSN). These sites make up the majority of search traffic globally (with google as the biggest player), so much so, thats its not worth devoting time to any of the others.
A further reason is that many of the other search engines are outsourcing their search to these three big players, i.e. alta vista, the big name in search when I first started using the internet, runs off the yahoo! engine. And apparently, AOL uses google.
In a more personal example, an associate of mine operates a regional information/business directory site. The search function on that site uses google's search technology. This is the case with many sites, and the big players are making it easier and easier to integrate their technology into other sites.
So, if you get an email from a company, or come across a site that offers to submit your site to hundreds or thousands of search engines for $X, you need not be impressed. You can manually submit to each of these major players within a few minutes and it is absolutely free.
To add your URL to google, go to
http://www.google.com/addurl/
To add your URL to Yahoo!, go to
https://siteexplorer.search.yahoo.com/submit
To add your URL to Live, go to
http://search.msn.com/docs/submit.aspx
