Establish yourself as an authority on the subject by offering free advice on the topic. Once you put together some valuable information, there are plenty of excellent ways to get it published to your targeted audience. Offer your point of view to your favorite Discussion List. Usually delivered via email like an ezine, a discussion group, or list differs from an ezine in one major way - they allow you to voice your opinion, usually through a moderator. There are discussion lists on many subjects and they're a great way to get answers to specific questions about your particular area of interest.
Discussion lists hold a marketing value similar to that of newsgroups.
You help others while your sig file does your marketing. Discussion groups are much more powerful though, since they are delivered to a targeted audience, rather than having to find them. Many discussion groups offer advertising as well, usually in the form of sponsorships. This is a moderated, global discussion on internet advertising, marketing and online commerce. If you're interested in online marketing, I highly recommend you check out this list.