Welcome to the board discod. If the site in question is the one in your profile I think all the ideas you suggested will work very well for you.
1. Become a directory of information: Probably one of the most important and effective forms of promotion. If you provide your target market with all the information they need and are looking for relating to your field than they will never have a need to go anywhere else once they find your site. They will come back and back and probably make a purchase eventually.
2. Develop an affiliate program: This could generate some income but I wouldn't expect a fortune off of it. I am sure there are hundreds of personal sites and local clubs relating to your products that you could potentially sign up as affiliates but it probably wouldn't be a product the general public would use.
3. Use your large database of customer email addresses: Yes! Your past customers are more likely to be future customers. If you send them a monthly newsletter with a coupon for $5 off their next purchase or something they will probably buy from you again. You would also keep your name fresh in their mind through the frequent contact.
4. Flash or Video: Some videos on the site would be an added feature that you could include to keep people coming back. I would stay away from flash though.
It looks like you are on the right track with these ideas. You could also try some different things like sponsoring some contests, giving the heads of some local clubs a big discount on a purchase hoping they will pass the word on to their members, and many things like that.