I’ve written about Truecrypt before. If you need cross-platform full-disk crypto, here’s an alternative I found recently. Veracrypt is based on Truecrypt, but since you can’t fork it without a name change, it has a different name.
I haven’t messed with it yet myself–yet–but if you need this, you probably already know it. And, for the record, I don’t believe there was any conspiracy against Truecrypt.