Encryption For Business (e.g. Medical Billing)

7-Zip (can also AES encrypt files)
http://www.7-zip.org/

AES Crypt (individual files)
https://www.aescrypt.com/

GNU Privacy Guard
https://www.gnupg.org/

List Of Top 24 Free Tools For Data Encryption
http://www.gfi.com/blog/the-top-24-free-tools-for-data-encryption/

TrueCrypt Final Release Repository
https://www.grc.com/misc/truecrypt/truecrypt.htm