Is there a way to create a link (perhaps an "activity" stream?) that lists all recent topics that haven't been answered to yet?

It's not possible out of the box but there's a 3rd party app for this in our marketplace 

 

You can also filter each forum to show just unsolved posts.

Great, thanks a lot for providing two different solutions. I'm going to have a look at that 3rd party app, it looks like what i'm looking for.