I have been submitting my website to hundreds of free business directories. I have heard that this is good, and I also have heard that this can be bad. The place I use is http://www.addurl.nu. What are your oppinions on this subject?
"Most" directories don't give much weight SEO wise in the search engines, the best backlinks are natural ones from sites that are relevant to yours.
Which are not that easy to get. In any case, directory submission is an ok method to build some decent permanent backlinks, but as ssandecki said most of the directories won't give a good boost.
Not from free directories. Google is on a paid link jihad and "directories" that are no more than glorified pagerank brokers aren't going to help you. It would go against Google's ethos to allow 3rd party links to harm your rankings. Unless there is a really eggregious pattern of paid links, I'd think that at most you are wasting money on them and the links are simply ignored/discounted.