Basecamp, GitHub and JIRA are great for collaborating, but none of them natively supports resource forecasting and time tracking. The browser extension allows Basecamp or GitHub users to manage the inputs required to forecast resources and track time . . . all without having to leave Basecamp or GitHub. JIRA works the same way except that it uses Atlassian's add-on framework.

Related articles:
Browser Extension Account Set-Up (for Account Owners)
Download and Configure Chrome, Firefox & Safari Extensions
Help, the Browser Extension "®" is Missing!
GitHub Integration (set-up)
JIRA Add-On is Installed, Now What?