WinZip is a great Windows tool for working with compressed files. The main problem (IMHO) is that it doesn't intuitively support .tar/.gz compression. Since gzip gets better compression than zip most of the time, the app I want to work on would do a better job. Users would be able to decompress (and create!) both .zip and .tgz files in the same fashion.
More info on WinZip: http://www.winzip.com/
The tentative name for my JOS version of this app is Zip.
-- MasonZhwiti