I've been using WinZip for many years. I could almost get by with the built-in zip feature in XP, except that it cannot be automated by scripts.

I recently started using the 7-Zip File Manager instead of WinZip. In addition to supporting .zip compression (with a better compression ratio than WinZip and PKZip), 7-Zip supports several other compression formats. 7-Zip's native 7z file format offers a high compression ratio and optional secure encryption.

Since 7-Zip is open source and scriptable, I don't expect to use WinZip anymore. See 7-Zip's on-line help for details about the command-line interface.

Download the 7-Zip File Manager here.

When I need to programmatically unzip .zip files, I rely on the excellent #ziplib .NET Zip Library.