The developers of TrueCrypt, open source encryption software capable of encrypting whole hard drives have posted a message on their site as of yesterday saying that the software is no longer supported and urging migration to other tools.
TrueCrypt is used by many people to strongly encrypt their data. This is useful in many fields including journalism for those working on sensitive stories. I've played around with the tool myself in case I should ever need to use it.
Theories as to the abrupt announcement vary, ranging from something being found in the well-publicized crowd funded security audit to questions of whether the site was hacked to security researcher Steve Gibson's assertion that the developers may just be tired.
Until someone knows what's actually going on, it's probably not constructive to comment on rampant speculation, but I can point you to an alternative.
I don't have the technical expertise to evaluate the security of any given encryption platform, but Steve Gibson recently stated on his Security Now! podcast that AxCrypt was a "perfect, clean, simple encryption tool."
I can say that I have used this in the past and in many ways, AxCrypt is easier to deal with than its TrueCrypt counterpart. After installation, the user gets a new AxCrypt entry in their right click context menu that allows them to encrypt files. Clicking the encrypt button, a user is prompted to enter a passphrase. The next time they open the file, they must put in the passphrase before gaining access. The encryption puts the file in a different format. This means if you encrypt a Word document, the document will no longer be accessible through the open menu in Word. You must open the file and input the passphrase from the folder the file was saved in.
Unlike TrueCrypt, AxCrypt doesn't offer full disk encryption, opting instead to encrypt files and folders you specifically select. Those looking for full disk encryption on Windows are pointed by the TrueCrypt website to Microsoft's BitLocker. Unfortunately, however, this is only available on the Ultimate and Enterprise editions of Windows 7 and Windows 8 Professional and above. Mac users can turn on FileVault. If you need encryption, I would recommend doing this because AxCrypt doesn't appear to have a Mac version. It's also free and saves you from having to find another solution.
For those looking for a deeper analysis of the TrueCrypt situation itself and the many possible theories, I would point you to this Forbes article.