You are going to require a feed URL for your Google Groups. To subscribe to the XML feed of your Google Group or just get the feed URL, click on the XML button which is located at the lower part of your Google Groups page. Click on “15 New Messages” under RSS 2.0 or just copy its link.
Now fire up Yahoo Pipes. You’ll need to create a pipe that will collect the data from the XML feed for displaying information on your popular posts widget. It will actually take the most recent Google Groups XML feed and terminate the rest, filter out the links that aren’t to be included and and lets the visitor land on the post page. Or you can simply clone this pipe. Now enter the feed URL that you just copied from your Google Groups into in the Fetch Feed box. Now, you’ll see a filter in the central part of your pipe. You’ll need to enter the constraints for showing the required posts in your Popular posts widget. In this pipe, it is according to the date permalink model. In the loop box in the upper right part of the pipe, enter your website URL in the string builder so that when anyone clicks on any link on the popular posts widget, he/she can land on the exact page.