Link and a bit more technical details:
https://www.socialfortress.com/
Social Fortress currently provides transparent client-side encryption and decryption within Facebook, Google+, Thunderbird and Outlook for your messages and photos.
When you download and install Social Fortress your plugin is customized to sync with just your account and the key management server. This unique plugin is authorized to request keys for messages for your Trusted Contacts and generate new keys associated with your account.
The keys are generated in parallel on the client and on the key management server. They are always rolling forward and are synced with the key management server in real-time utilizing a few unique variables within your custom plugin and a few generated randomly each time.
No two messages are encrypted with the same key and keys are only stored in memory during the encryption / decryption process. Every time a message or photo that has been protected is viewed, either by yourself or others, authorization to that messages key is requested from the key management server.
Your Trusted Contact list is managed globally by connecting with other users through Social Fortress. Within Facebook all of your friends are initially treated as Trusted Contacts and you can easily remove individuals from this list with the click of a button.
Social Fortress uses AES-256 CTR for the encryption and communicates over a 256 SSL stream from your device to the key management server. The data in this stream is also encrypted using aspects of your customized installation.
The technology for web services (Facebook, Google+) operates as browser plugin for Firefox, Chrome and Internet Explorer[1] and independent of any service's API.
The technology for Thunderbird and Outlook is a separate plugin which requires installation.
We integrate transparently into the products we support so the user experience is exactly the same. No extra clicks, no confusing decisions and nothing extra to learn. We designed Social Fortress to be used by individuals who don't even know what the word encryption is.
Within every environment you have the ability to enable / disable Social Fortress protection with the click of a button or using a keyboard shortcut (CTRL+Q). This only disables the encryption functions. The reader is always on so messages and photos protected by your friends appear normal without you having to protect your own. It's like having Flash or PDF Reader once it is installed you don't ever have to do anything again.
If your device becomes compromised / lost / whatever you can login to the site and disable all active installations in two clicks and this will not affect previously encrypted messages as we just disable authorization access to your old plugins and have no need to change any previously generated keys.
We also support other services but have yet to make them live:
Skype Chat
Twitter
mail.yahoo.com
Gmail.com
Chatter.com
Yammer.com
Blackberry Native Email support
[1] The IE Plugin is not currently part of the public beta.