Mozilla's new Addon Collector lets you bundle, subscribe to addon packs
Install Collector and sign in to your Mozilla account. You'll find the login form on your add-ons menu under a new Subscriptions tab. Once you've signed in, creating a pack is as simple as selecting your favorite addons and pressing the publish button. The button also lets you fire off a recommendation via email, though it's totally DIY right now. There's no external address book support but the form will ask if you want to remember the addresses you enter.
Private collections provide a good way to keep your personal (or team) Firefox installs running in step. Set up a subscription, and new additions are automatically checked for at the interval you specify.
Want to make your pack a collaborative effort? You can invite additional publishers (who can add and remove add-ons) and managers (who can additionally manage users and collection settings).
Options have also been added to Mozilla profiles to display your collections on your personal page.
The Downloadsquad 2009 Summer Collection will be hitting the runway soon, so stay tuned!