A new Todoist Firefox sidebar is now added which offers following features:

• A toolbar button is added, clicking on it will launch a minified version of Todoist
• Add links with a single click
• Gmail integration: Add emails as tasks and view them quickly
• All features from Todoist
• Shortly said: The sidebar makes it possible to view tasks in a split-second!

Get the sidebar from the info page.

You can also check out the blog post named Getting organized with Todoist sidebar.