Here are some useful tools that allow you to uncompress rar, tar or zip files online. No need to have a program installed to unzip for you. Unrar, Unzip, Ungz and Untar with just Chrome or any browser you have.
Convert files online tool allows you to convert RAR to zip file.
A neat tool called Wobzip let’s you unzip and unrar all entirely online. No need to have Winrar, it’s a must have if your work or school computer won’t let you install winrar.
I just unzipped a rar file just now, and I can say it for sure works.