Update (3rd May 2013): This extension now supports all file types supported by Google Drive Viewer. Enjoy!
Google Docs has just announced support for two more file formats: .ZIP and .RAR. This enables you to open online .zip and .rar files using Google Docs Viewer without downloading. Gmail users can also open zip and rar attachments directly.
Google announced this in a blog post, “This will bring up a view that includes all of the files in the archive, the file types, and the size of those files.You’ll be able to View items supported by Google Docs Viewer and Print (PDF) those that we offer PDF support. Save to Google Docs and Download appear for all files.”. Hence, you can view contents of zip and rar files before downloading.
I have created an extension for Google Chrome, which enables you to open online zip and rar files in Google Docs Viewer. Install this extension from Chrome Web Store. Whenever you find direct link to a zip or rar file on any web page – simply right click on it and select the option “Open with Google Drive Viewer”. This will open that file in Google Docs directly.
Also try: gPDF