No follow links don't add any value to your website. It doesn't effect your SEO or search rankings in any way, but some people will say it has a very tiny, minimal effect on it. However, you should never avoid it, and I'm sure you know that by now. Google looks for a certain percentage when it comes to Nofollow links, they can determine who's using blackhat techniques if they don't have any nofollow links on their website and bring down the penalize hammer. I believe the percentage is anywhere near 15-24 percent or higher. Anything below that will be dangerous to your website.