Been extra interested in online privacy lately and ran across a few things that looked pretty interesting.
The first is "Blackphone" (https://www.blackphone.ch/), a smartphone designed to be as protective of your privacy as possible. It runs a modified version of Android and includes a number of communications apps designed to keep you conversations private. I'm still learning about how they do this (in particular how they handle potential baseband processor firmware issues, etc.) but from what I've been able to discover so far it's the best implementation I've seen that still lets you talk to people outside of secured networks.
Also it's called the "Blackphone", I mean come on, that's pretty bad-ass.
Reading up on the Blackphone lead to some interesting software as well. The first is "Silent Circle" (https://silentcircle.com/) who produce a number of communications applications (voice, video text) that use encryption and private networks to keep the information exchanged private. From what I've been able to discover so far I think their approach is valid and the nice thing about their products is that they are cross-platform, so they can be used to communicate over existing networks and devices. This of course does open an attack vector (part of why the Blackphone exists) but it's still significantly better at protecting privacy than using the built-in features provided on most devices.
During this time I also learned about "Spider Oak" (not sure if there should be a space in there, https://spideroak.com) which provides encrypted online backup and file sharing. Other products like Dropbox can encrypt the data you store in them but SO's approach is more sophisticated than others I've seen in that it uses unique encryption keys for every file stored, so it's possible to selectively share individual files without providing the ability to decrypt the entire backup. They also have several measures to make the encryption particularily hard to crack and implement a strict zero-knowledge policy that prevents their staff from having the ability to access data stored on their servers (there are some situations where it's theoretically possible for SO staff to have access to some of your data, but when this occurs their software is very explicit about entering this state before you do it).
SO also maintains a Github repository (https://github.com/SpiderOak/) of open-source code they use and create for the service (they intend to open-source all their code eventually).
This is where I found crypton.io (https://crypton.io/), which looks like a promising general-purpose framework for creating zero-knowledge web applications. I haven't had a chance to play with it yet but if you are buildng something that stores people's information on the web it's worth taking a look at.