This is a very basic program for using GZip compression and decompression.  It allows you to select a file and a folder and it will compress the file, saving it with the same file name and adding a .zip extension.  The same program can be used to reverse the process, unzipping a file back to the uncompressed file.  There is very little error catching (zip files with other formats, files that already exist, etc) but it is a good base on using the compression available within the .Net framework.

Download the VB.Net 2008 SP1 source code: code-gziptestapp.zip

Screen shot:

This source is released under the GPL.