Google itself is responsible for approx. 40% to 60% of the total traffic in the USA, it varies depending on the keyword used. It is very difficult to determine precisely how much traffic is generated from each of the directories and search engines below but I am sure that you are missing a large share of the traffic by not being listed in all major directories.
• Most of these directories are human edited, so it is important to spend considerable time making the submission properly and accurately in order to be approved.
• ONLY submit your web site to directories and crawlers in which it is not yet found (just make a search for your domain on each directory before submitting, if it is already listed, do nothing).
• These are all trust web sites which are not going to publish your email or share confidential information but they, sometimes, do send newsletters, which you can opt-out with no problem.
• The links provided accept free submissions and a link back is also not required.