Effect on page rank of submitting sites to Web Directories?

Hello Friends,
I want to know what is effect of submitting our site to Web Directories which ask us to link back to them ? Does it anyway harm our site's page rank? I am asking this, bcoz i want to know whether google consider this is as spam ?

Also please let me know whether we should use link farming?
Thanks,

You can use web directories that dont ask you to link back to them instead.

I dont think google will consider that as spam, set up a links page on your site and respectivley link back to sites that are relative to what you site is about or does. This is a great way to generate back links to your site. The more related and popular the better.

I don't submit to sites that require a return link or small fee if no return link is posted. And, I have submitted my site to over 400 directories. All free, one way link directories. Personally, I would stick to these types of directories if I were you and not get involved with reciprocal linking unless it is a niche directory whose content is similar to your website content and you want to include their link on your site.