Gone - An ephemeral to-do list
OKRStudio - Connect Trello cards to OKRs. Manage OKRs inside of Trello
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
OKRs.app - Reach your personal goals with OKRs
Check - Check is a unit testing framework for C, which runs on environments such as GNU/Linux, GNU/Hurd, BSD, and Mac OSX.
Perdoo - OKR methodology, software and coaching