If you take a look on the right side of the page, you’ll see a Mozilla Labs design challenge logo. That’s because we’re running a Summer 2009 Design Challenge, which is currently open to submissions! The topic is “Reinventing Tabs in the Browser” (a topic I am very interested in).
Click the logo in the right sidebar (or click here) to go to the page with the detailed description of the design challenge, including the deadlines and the instructions for submitting your concept. Go check it out!