Hello,
I totally agree with the fellow frieds who have suggested that it depends on your requirements. I personally do not have any of my websites in the Yahoo Directory and not even in the DMOZ direcotry but still we enjoy the top listing on all the major search engines for our choice of keywords.
So, the major thing I'll suggest to you is to make your site so attractive and addictive by adding articles, useful content so that others automatically start linking you.
Sincerely,
Ajay Chadha (Director)
Chadha Software Technologies
Search Scripts - Scripts Resource Directory