The document discusses various marketing channels that can be used to promote a business or product. It provides 19 different channels along with examples of companies that have used each channel successfully. The channels include viral marketing, public relations, search engine marketing, social media ads, content marketing, email marketing, engineering as marketing, blogging, business development partnerships, sales, affiliate programs, existing platforms, offline events, speaking engagements, and community building. The document also includes examples and advice from the founders of Hubspot on their approach to inbound marketing.