Reaching The Inbox - A free step by step guide to maximize email deliverability
Attributer - Know what marketing channels are driving customers & revenue
Indie Channels - Distribution channels and marketplaces for makers
Sidemail - The simplest way to send transactional emails. Sidemail makes sending transactional emails trivial, it's perfect for side projects, MVPs or the next big thing.
Intercom on Marketing - The marketing book for startups
Makerbook - A directory of the best free resources for creatives