Please encrypt your communications whenever it's possible. Not because you have something to hide, but because there are many entities handling our private data that do not necessarily have their interests aligned with our personal privacy (probably an understatement).
For text messaging (Android only) I use the excellent 'TextSecure' app, which is an open source drop-in replacement for the standard messaging app on your phone. You can read more about it at http://www.whispersystems.org/
The aforementioned Whisper Systems also has an app called 'RedPhone' for secure voice, but I have yet to try it. If anyone uses it, I would be very glad to hear your opinion.
I use Redphone almost everyday. They now have global coverage except for most of the Middle East and some parts of Eastern Europe. The Egyptian server apparently doesn't relay so well either last I heard on the mailing list.
Works as advertised in China which is great success for businesses worried about their blackberries or iphones being exploited by industrial espionage.
Another bonus is moxie is considering moving everything over to voip so you won't even need a cell contract (since google voice numbers don't work worldwide). Move around the city like a ninja using wifi
For text messaging (Android only) I use the excellent 'TextSecure' app, which is an open source drop-in replacement for the standard messaging app on your phone. You can read more about it at http://www.whispersystems.org/
The aforementioned Whisper Systems also has an app called 'RedPhone' for secure voice, but I have yet to try it. If anyone uses it, I would be very glad to hear your opinion.