I signed up as an expert on yahoo last week, i have only answered three questions, however two of them had links back to my site if they needed more help. looking at my logs, i noticed that i have had 14 people visit my site from experts.yahoo.com! And my category is small, only a dozen questions asked in the last two weeks!
This is a great way to drive targeted traffic to your site, and recive long term customers! Goto experts.yahoo.com, and sign up as an expert. Dont try to spam the system, but rather help people, if your site does offer more help, put a dirrect link to where they can find more help.
This may take some time, dont expect to recive hundreds of visitors a week to your site this way, however im sure you can recive some great traffic, and hopefully make some sales as an yahoo expert.