Gnu Privacy Guard (GPG, the free/open version of PGP) relies on donations to pay developers to keep the project alive and viable; as one of its millions of users, I am grateful and indebted to the people who keep it alive and that's why I've just donated to the project.
gnupg is especially important as it is is both free of charge and freely licensed. That second point is critical, it means that gnupg is open to scrutiny from any expert to help ensure it is free of back doors or other problems that might compromise its effectiveness. For users of alternate operating systems like BSD and Linux, it is often the only choice for certain applications of encryption. Thankfully, it happens to be a usable and useful one that interoperates with the commercial, proprietary choices available to users of more mainstream operating systems.
GnuPG and g10code [Werner/GPG]