I didn't install any of them, of course, but somehow, other people's actions were showing up on my News Feed.
Turns out you can block all updates from these apps by surfing to their main page, and clicking on the Block app link. It's located at the lower right corner, below the "Afraid of abuse by this application?" question:
If you had previously blocked an app, Facebook will inform you. This step will also work for other abusive and spammy apps.