The Yahoo! Directory is the most powerful paid directory on the web. If you are serious about getting good rankings in the search engines then you should definitely submit because if you get accepted the link will count as a true vote of confidence towards your site and it will help you to build up more trust with all of the engines.
In order to get listed you need to pay a fee of $299 per anum to have a Yahoo representative review your site to make sure that it meets their requirements. Providing your website is a genuine business website then you shouldn't have any problems getting listed however do make sure that you read the Yahoo Directory terms of service before you submit, just to make sure that your site is definitely suitable.
Once you have read the terms of service and you are sure that your site is suitable get ready to submit, create an objective description of your company to use for your directory listing, get your credit card ready to pay the $299 review fee and then click on the link below (you need to create a Yahoo account if you don't already have one, instructions are given on site).
Once you have submitted, Yahoo guarantee to review your site within 7 days, Yahoo will select the most appropriate category for your site and when it is first listed you will also be featured in the What's New category of the directory which gives you a good amount of traffic to your site. You will have to pay the $299 every year to make sure that your website still meets their requirements.