DIRECTORIES: Yahoo is unquestionably the highest traffic directory on the net today. Tomorrow, maybe. Listings there are no longer free for this type of site. Check the T & C to see what the current fees are. You will pay for a REVIEW of your site with no guarantee that it will be listed. A good listing in Yahoo should far outweigh the cost but a poor listing is money wasted. Looksmart is another large directory but it's importance in the search world is fading. They also feed MSN which is about the only thing of value they have left to offer.
There a MANY niche directories on the net. Some are gambling related and some are general. Some of the better gambling related directories to get listed are in no particular order: Casino-on-line.com Gambling.com, Askgamblers. Listing in most of the directories will be free but you will be required to provide a link back to the other site.