How to GPG text on Unity?

Pyrite was written just for this purpose. It's not packaged yet -- so not in the repos; you'll have to follow a few instructions to download and extract it to a location of your choice manually, but it works wonderfully IMHO. (I would say that though.. since I'm the developer.)

As bessman mentioned, seahorse-nautilus is the way to go if you want to asymmetrically-encrypt files in the file browser. (In addition to text, pyrite can do symmetric & asymmetric encryption of files, but it's not integrated with Nautilus.)

Finally, check out the answer on this older question for more details on setting up gedit with gpg.

For email, there is a thunderbird addon called Enigmail which performs email encryption or signing, and is quite nicely integrated. Install it from the Software Center or with sudo apt-get install enigmail.

Seahorse still exists (it is called "Passwords and Keys" if you search in the dash), but does appear to have lost built-in support for text encryption/signing (I think - I don't have a GPG key on this system to test with).

This thread gives the syntax for signing, encrypting, verifying and decrypting text in the console with the gpg command.

This answer explains how to add gpg integration to gedit, although I must admit I was expecting to find better plugin support for encrypt/sign in both gedit and tomboy notes without obvious success.

You can integrate Seahorse with Nautilus by installing seahorse-nautilus. It will allow you to encrypt and decrypt files and folders by right-clicking them.