The Activity Stream report allows you to view the recent happenings on projects, tasks, bugs, etc. that you are assigned to, manage or follow. This report can also be placed on one of your dashboards. An example is shown below:
As you can see the history is grouped by each object and the recent happenings for that object are shown. You can click on View All to view all activities since that object's creation. There is also a comment area where you can put in your comment. And like any other report, you can customize what you wish to see.