Yahoo! doesn't guarantee inclusion.
I can submit your site to 250+ of the most used search engines for $25. You can also submit them yourself for free but it will take a while! If you do it yourself remember to include sites like
www.google.com,
www.altavista.com,
www.msn.com,
www.alltheweb.com etc etc. Google is the largest and most used search engine.
As for paid inclusion there are a few options available to you.
1. You can pay for inclusion in some search engines which give a guaranteed update time, usually once every 24-48 hours - this allows you to work on your page optimization and get quick feedback rather than waiting 4-6 weeks before finding out if your SEO (Search Engine Optimization) was fruitful.
2. You can go the PPC (Pay-Per-Click) route where your link is guaranteed to finish above non-sponsored results and you pay everytime someone clicks on your link.
(snipped by Oli)