Encore Vehicles posts messages to rec.auto.4x4 and rec.auto.jeep among others. They know potential clients will see the message and follow the link to their website. Best of all, the prospects who come to your site via Usenet are already prequalified 3 times once they contact you. Of course, these groups are very active, and so the messages get cycled out after a few weeks. Some are archved, but to stay in the active files, you need to post at least monthly.
Some groups require weekly posting and others are even more active.
The busier the group, the more often you need to get your message in there. Harvest email addresses from every possible source and encourage surfers to sign up for something truly useful or entertaining every month. It works like this. It has headlines of interesting stories or describes something else they want, and then links to your site for the details. Whether you offer recipes, lawyer jokes or stock advice, make sure it is really something they want.