A common link building task is to post blog comments on blogs with the dofollow plugin installed. Since blogs have the NoFollow attribute on links in the comment area by default, linkers search for ‘dofollow blogs’ to get inbound links that count (that pass PageRank).
To be clear, there is no such thing as a “dofollow link”. It’s simply a link that does not have the NoFollow attribute. For more on that, see the NoFollow Attribute section in the Link Building 101 post.
There are browser plugins that will tell you whether links are dofollow or nofollow, and there are also Do Follow Blog Directories that will give you a list of blogs that offer dofollow links in the comment section…