Directories
These are similar to search engines but instead of relying on automatic algorithms, directories have actual human beings checking websites! Yahoo!, The Open Directory Project and JoeAnt are all human edited directories.

The main difference with directories over search engines is that directories only list the home page and the information they file for your site is either the information you give them via your submission, or a description written by a directory editor.

The 2 most important directories to submit to are;
Yahoo! - http://dir.yahoo.com/ (Costs $299 for commercial sites)
The Open Directory Project - http://www.dmoz.org (Free)

DO NOT submit more than once during a 3 month period, and do not submit one website to multiple categories. Read the submission guidelines for each site if you're unsure about anything.

PPC

PPC ads appear like search engine listings but are actually paid advertisements. The highest bidder gets the highest position. Yahoo, Google Adwords and Miva are all examples of PPC engines that you can join. The advantages are that you can get a Number 1 listing almost immediately, the disadvantage is that you have to pay for every click through.

Google AdWords is not strictly a PPC Engine but it is usually lumped in with the others as you still have to pay for each click you receive.
You can find loads of different Pay Per Click search engines here - http://www.payperclicksearchengines.com - infact, there's hundreds