Mozilla Labs
Thunderbird Contacts
FreeThunderbird Contacts Unifies Social and Email Connections
Windows
Mozilla Labs: Rainbow
FreeRainbow for Firefox Enables In-Browser Media Recording
Windows
Firefox Share alpha
FreeFirefox Share: Quick Link Sharing Extension
Windows
Mozilla Contacts
FreeThunderbird Contacts: Unified Address Book with Social Integration
Windows
Add-on Builder
FreeStreamline Your Add-on Development Process
Web Apps
Prospector: Speak Words
FreeProspector: Faster Site Navigation for Firefox
WindowsMozilla F1
FreeShare links to social networking and e-mail services from within Firefox.
Windows
Mozilla Lab Kit
FreeGet Mozilla's Latest Browser Experiments Automatically
Windows
LessChrome HD for Firefox
FreeLessChromeHD: Maximize Screen Space for Browsing
WindowsAdd-on SDK
FreeComprehensive Overview of Add-on SDK for Windows
Windows
Prospector: Find Suggest
FreeProspector: Smarter Search Suggestions
WindowsAdd-on Builder
FreeFirefox Add-on Builder: Simplify Extension Development
Windows