The Forums app contains several special widgets that can be placed in the header, footer, or sidebar.
The popular now widget references the popular settings option in the Forums app.
The topic and post feed widget are particularly powerful as they let you create a customizable feed of forum activity anywhere you might like to place it on the Suite. You can place these widgets on any area of the Suite - not just the Forums app. So you might choose to put a feed of topics on your Gallery page to cross-promote areas of your community.
With any widget just access the control panel using the icon on the left of the screen and drag it where you like. You can then edit to get more options. Some options for the topic feed might include:
Be creative with the filters and option to highlight many types of content.