Swizzler

Swizzler is the simplest, most elegant solution for encrypting files and folders on your Mac. Swizzler allows you to encrypt and decrypt files and folders with a single click from within the finder. The free version of Swizzler is fully functioning in every respect other than that it can only encrypt individual files which are smaller than 100k in size. There is no time-limit on it's use, if this is all the functionality you need, then Swizzler is free. To encrypt folders and files of any size you will need to upgrade to the full version.

Limitations:

The Trial version can only encrypt and decrypt individual files (not folders) upto 100kb in size.