Following the Extend Firefox 2 contest that ended a couple of months ago, Mozilla Labs has announced Extend Firefox 3, a competition for developers to create or update their Firefox extensions that use some of the new Firefox 3 capabilities.

Three winners in the new extension category will take home an Ultimate Firefox Developer Kits including:

• Travel and accommodation to a Mozilla Developer Day of the winner’s choice, anywhere in the world
• Development gear, including a brand new 13″ Macbook Air with VMware Fusion and ActiveState Komodo
• Firefox Ogio Messenger Bag stuffed with t-shirts, books, stickers, mugs, and more

Six runner-ups get the stuffed Ogio Messenger Bag, ActiveState Komodo and a mug.

Three winners in the best updated category will get a 15″ MacBook Pro with VMWare Fussion and ActiveState Komodo, along with the stuffed Ogio Messenger Bag.

The competition is opened to residents of almost every country in the world and runs until July 4th, 2008. Winners will be announced around July 31.

Official rules.