Google Groups is one of the most popular way to have discussions with people. You can also have private Google Groups which can be used to share ideas or discuss anything between a group of people.
Since Google Groups had launched, there were hardly any changes made to the UI. However, it looks like Google is now revamping the groups and adding a more user-friendly UI to it. At first glance, the revamped Google Groups show hints of Google Wave, the failed Google product which is now rechristened as Apache Wave.
The new UI, has a sidebar which allows you to quickly navigate between groups and recently viewed topics. The main topics area has been revamped too to make it easier to browse and reply to threads. The new UI also has a new Overview section which displays the topic summary, links used as references in the post and the conversation thread.
Overall, the new Google Groups UI is pretty easy to navigate and is really fast. You can give the new Google Groups UI a test by visiting this page and clicking on the "Switch to new Groups" button. You can also watch a video embedded below to see what the new Google Groups looks like.