Mozilla Labs introduced a new project called Weave. The goal of this project is to enhance the Firefox user experience, increase user control over personal information, and provide new opportunities for developers to build innovative online experiences.
Weaves main purpose is to synchronize metadata across your computers and share it with your family and friends. Metadata (bookmarks, history, saved passwords, persistent cookies, customization, preferences, etc.) will be synchronized with this feature. The developers are also very concerned about user privacy so you don’t have to worry because Weave will have several encryption methods to chose from to secure your private data. Weave will also have a “admin page” if you will, so you can select who can see what of your data if you chose to share it with family, friends and third-party members.
The development team wants to build a secure basic framework which can be upgraded with many tools and APIs to extend the user experience overall (something like Mozilla Firefox does with add-ons).
Note that such a thing already exists as an add-on for Mozilla Firefox and is maintained by Google - Google Browser Sync, but is not so open as the Mozilla project.
The project is currently in development phase - Weave 0.1 (released on 21th December 2007) and for now only includes bookmark and browser sync. Therefore the project should be only used for testing purposes.
Initial Roadmap
Weave 0.1 (December 21, 2007)
- basic framework and server-side in place for testing and experimentation
- authentication with a single online service provider (e.g. labs.mozilla.com)
- bookmark and history synchronization to the server from multiple clients
- default encryption of all user data with a placeholder algorithm
Weave 0.2 (Early 200 
- initial Web service APIs for developers to build on
- user controls and ability to delegate (and revoke) access rights to specific bits of browser metadata
- UI to enable sharing on applicable interfaces
Getting started:
The first thing you will need to do is install Mozilla Firefox 3 Beta 2 (look post “Firefox 3 Beta 2” for more information) since it only works on that. Next you must sign up for a new Mozilla Service account and then follow the instructions which will be sent via e-mail. After you install the prototype just follow the on-screen instructions and you will be set to start testing the new product.
Original post at Mozilla labs:
http://labs.mozilla.com/2007/12/introducing-weave/
You can also read the preview on arstechnica.com
Thanks for the heads-up!