Firefox: Mozilla knows we often reach out to our contacts through our browsers. So the Firefox maker has crafted an experimental tool to make, for example, filling out "email this" forms easier by importing contacts directly into your browser.
At the moment, the practical use of Contacts is limited to importing contacts from your desktop, Gmail, Twitter or weblog Gravatar sign-ons, and then simply listing, searching, and easily auto-filling email addresses into websites that ask you for them, whether to send an article, sign up a friend or otherwise ping somebody. It searches and narrows your contacts as you type, a la Gmail's auto-complete address fields, and that's pretty handy in itself.
Mozilla, though, has grander plans for managing your contacts inside your browser than just helping you send funny articles to your friends. Eventually, you'll be able to authenticate websites to access your browser-stored contacts, rather than handing over your Gmail or Twitter username and password to every site that asks for them — and that's a lot, these days. Here's Mozilla's pitch:
Every desktop operating system, and hundreds of web-based service providers, has some way of representing "who-you-know". Managing all of this information can be a lot of work. There are multiple copies of your data, and they are inconsistent and disjointed.
This information is also special, because it represents the boundary between "my data" and "your privacy". When you disclose your friends' email addresses on a website (maybe you want to invite them to a cool new site you just joined), you are trusting the website to keep that address private. At most sites today, you do this by sharing an entire contact list from some other website (say, your Yahoo address book), and don't have much ability to restrict what information gets shared. The disclosure of your friends' contact information is an important step: we think you should be in control of it.
Contacts is a free download that should work anywhere Firefox does. It's a Mozilla Labs Experiment, and not "production-quality code", so expect to see glitches and bugs from time to time.
Contacts in the Browser [Mozilla Labs Blog]