Directory submission is still the best method to improve your search engine ranking and page ranks. Its important to have a good list of high PR search engine friendly do follow directories list that you could use to submit your websites to. Below is a good list of high PR dofollow directories that i have verified.
If you want to learn more about nofollow and dofollow backlinks and the difference between the two, this article could be helpful to you. Basically, dofollow links are the ones that transfer the link juice to the next page and you should be ideally looking forward to gaining good referrals from such highly trusted websites or directories with a dofollow backlink.
Below is a list of resource and feel free to add your recommendations in the comment section and I will try to get them included in the list, just remember to post the URL as a non-hyperlink as the comments section is “nofollow”.
PR 6 do follow directories list:
PR 5 do follow directories list:
PR 4 do follow directories list: