Spreading the Word
I really like the advice Global Moxie has given their users for how best to promote their content management system, Big Medium. In their blog post, Psst... Pass It On! Spreading the Word about Big Medium, they talk about various way users can "spread the word" about Big Medium. They show a good understanding for how online communities work, including what you shouldn't do when marketing a product via a blog or forum.
Don’t be a zealot