Find it at http://www.codeplex.com/DotNetZip .
That's all in the v1.5 library, which is now released and final. 100% managed code.
There is also a download of command-line zip tools - if you ever wanted to be able to create, read, or extract a zipfile from a command-line, or from a batch file, the utilities in the release are really handy for that. In fact I used the utilities to pack up the zip library itself, for upload to codeplex.
Also, the library is simple to use within a powershell script, so you can manipulate zipfiles in powershell. Maybe I'll post an example of how to do this in the future.
If you want some background on the Zip Library, check out my prior posts on this topic. Just for your information, DotNetZip is licensed under the Microsoft Public License, which basically means you can use it free of charge, for any purpose, but there's no warranty. Check the full terms of the license on the CodePlex site.
As always if you have questions on usage, check the CodePlex forums.
The last bit of news is that DotNetZip is now donationware. I am now accepting donations on behalf of my favorite charity. and Yes, it is a real charity.