Many search engines have merged such as altavista and yahoo. While some remain free, others charge per inclusion to their site. There's two methods in which you can pay to add your site to their search engine: pay per click, which puts you in the top results, but makes you bid for the keywords, and guaranteed search enclusion, which gives you a payment plan so they'll include and crawl your set ever set interval of days.
Not everyone can afford this because there's a lot of competition for the keywords bringing the price very very high. If you can turn a profit, it is a wonderful tool because the more money you put in, the more money you get back. Usually a few companies dominate and others cannot compete with their bids but being carefully selective with your keywords and continuing trial and error may be well worth the cost.
Your site is added and crawled, lets say every 7 days so it updates the information. The more you pay, the more sites they add, the more chance that you'll be seen in miscellaneous searches. I have had very weak results in the past paying ask jeeves and excite, but I paid the minimal. 1 page. Bulk submits may render more profit, especially if submitted among various search engines.
If your not a business, it's unlikely that the traffic received will be worth the input, but if you're looking to put your page everywhere at once, you may think of it as an investment. Even if it doesn't return immediate results, you may have your link appearing in other sites and hightening your pagerank. It's worth the try if your serious about your site.
For a list of search engines and directories you can submit your site to, go to the education page. Before signing up to any service try searching the name of the service + "consumer reports", "ratings", or even "scam" to make sure they're actually performing a useful service. There a lot documentation on how to be successful in google adwords and overture so be sure to do your research; it could save some money and initial disappointment. Try sticking to the official site for advertising. There's many scams appearing in the paid results that love to say "we'll submit your site to a billion and a half search engines".