Hello mats,
I am newbie here and want to nkow that  Does Yahoo Directory listing is a free service?
Thanks in advance for your answers.

Yahoo requires that sites pay a Yahoo Directory Submit submission fee of $299 per year for Commercial sites.
While for non commercial websites submission is free.

There are two option for submit the site to Yahoo Directory.

1) Yahoo! Directory Submit (Paid $299)
2) Standard (Free)

For more information about Yahoo Directory listing, check the following link.

http://add.yahoo.com/fast/add?80940
http://www.search-marketing.info/directories/yahoo.htm