Avoid link farms by all means. They will
decrease your rankings in the Google
search results. Also, it is against
There are better ways to get high PR links
back to your website.
You have to keep this in mind:
Google wants your site to have text(back)links
relevant to the theme of your website.
So, whatever technique or way you do it
use textlinks in your bio-box if you submit
articles. Use text-links in your description
if you submit to directories. Of course the
text-link will have relevant keywords to the
theme of your website in it.