Encode and decode your files to and from base64 format with Quick Base64.
It's really fast.
Quick Base64 is a free and open-source application which encodes and decodes files into and from base64 format.
It is made to be fast, hence it's name (Quick Base64). It has a simple interface and uses drag and drop for most of it's commands.
It allows you to either encode a file to base64 or decode a base64 text to it's original file format.
Also, it is very reliable because of it's base64 detector which prevents you from decoding any ordinary text except text in base64 format.
Source code can be found at Github