productboard - Beautiful and powerful product management.
OKRStudio - Connect Trello cards to OKRs. Manage OKRs inside of Trello
ProductPlan - Cloud-based product roadmap software solution
OKRs.app - Reach your personal goals with OKRs
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.
Perdoo - OKR methodology, software and coaching