For instant messaging, I suggest using one-time keys which aren't stored and not keeping any logs. In effect, once your client is switched off, any data collected is impossible to be decrypted, since the keys are lost and you never knew them yourself in the first place. For data you want to hide, use TrueCrypt (or similar) to encrypt most of your hard-drive and set up two keys - one which unlocks the illegal data and one which unlocks the legal data. It is important that you keep as much of your mostly legal data under the first key and only store truly problematic data (like pirated mp3s, the map to your secret hideout, etc) in the other. It's really hard to fabricate a ton of clean data and I think it's best if you simply encrypt everything you can and keep a tiny portion hidden.