Google Docs already lets you view 15 types of files in Gmail without downloading them. Now they've added support for ZIP and RAR files. So if someone sends you a ZIP or a RAR file, you just have to click on “View” and you can view the file within the browser itself. This will bring up a view of all the files in the folder and what type of and size files they are. When you hover over the files, you'll get a drop down list of options to View, Save to Google Docs, and Print (PDF). You'll be able to view documents that are supported by the Google Docs viewer and print (PDF) those that offer PDF support.
Check out ZIP and RAR viewability in Google Docs
ZIP and RAR files embedded in other ZIP and RAR files also work. You can have a RAR file inside a ZIP file and you can just click on it to access the embedded archive. This feature is also available in Google Docs for mobile. For each supported file, there is a link that you can click on to view it. Google says that they're continuing to add more types of files to Docs. If you'd like to tell them what additional file support you'd like, post on their forums. To try this feature in Google Docs, click here.