productboard - Beautiful and powerful product management.

Froged - One click solution providing easy-to-use marketing, sales and support services to turn website visitors into happy customers.

Aha - Aha! is the new way to create visual product roadmaps. Web-based product management tools and roadmapping software for agile product managers.

Keep Your Friends Close - A free e-book about maximizing Customer Lifetime Value

ProdPad - ProdPad helps your team gather ideas, surface the best ones and turn them into product specs, and then put it all on a product roadmap.

Intercom on Customer Engagement - A book on how to create messages that drive engagement