Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Business Model Kit - Explore revenue models to make money with your idea
Slack - A messaging app for teams who see through the Earth!
Lean Canvas - Business plans take too long to write, are seldom updated, and almost never read by others but documenting your hypotheses is key. Lean Canvas solves this problem using a 1-page business model.
GrowthList - A crowd-sourced list of growth hacks
GLIDR Team Edition - Product Management Software, Reinvented