Zip and unzip components, along with other forms of compression and decompression.
[>] Active Zipper
[>] Polar Zip
Polar ZIP Component is designed to resolve all the issues regarding zipping and unzipping requirements. It includes 32-bit ActiveX control and DLL with numerous functions that give your application the power to create, update, extract, list, and generate password protected zip files.
[>] ZLib Compression Library
A DLL library (with VB code to use it) and an ActiveX control allowing you to compress and decompress using the algorithm from PKZip and gzip.

ZLib compression is also vital to the PNG image format, if you want to read it yourself.