Yahoo is one of the largest search engine in the world. There is something specifically that I should do in order for Yahoo to rank me somehow ? Or if I am just active and have a very good site it gets eventually listed ?
One thing to check is which "version" of your site Yahoo knows about. If Google knows about www.site.com and Yahoo knows about site.com (without the 'www'), that could be part of your problem. Because it is likely that you are building backlinks to only one of those two variations of the site name, if the other one is indexed in Yahoo, it will not register as having backlinks, and will be ranked lower. On page optimize first for the Search Engine then your site will become popular. Trust me. Your traffic conversion comes from the search engines,so properly optimize first to make the search engines happy. They will in turn give you good SE placement, then all else falls into place.
If you have extra money, i highly recommend you to try yahoo directory. For normal site $299 per Year. For adult site $600usd per Year. I'm sure it can boost your traffic and ranking on internet.