Calling GnuPG "email encryption software" really understates its importance. It's also used in countless applications to encrypt data at rest, and GPG signatures are used to secure the distribution of software. For instance, GPG is an essential part of the package managers of Debian, Ubuntu, and RedHat. Here is a link to the donation page: https://gnupg.org/donate/index.html
Email Encryption Software Relies on One Guy
Err... did PGP recently go bankrupt?
Edit: Crap, it's worse, they seem to have been acquired by Symantec. Is it still any good?