J-Pack SDK is a practical and interesting ActiveX component that gives the programmer methods to create and modify files in the JPack format (a compression format similar to GZip).
Once you have created the JPack file, it is very easy to decompress. From the different functions with which this J-Pack SDK component comes equipped, you can, apart from editing and creating, browse through the different files that make up the resulting JPack.
J-Pack SDK is also totally free, although the author asks for you to previously register on the website to start using it.