You can unsubscribe from future notifications right from your Notifications page in Podio. You can use this when you get a notification in your inbox about something that you wouldn't like to follow anymore.
When you've clicked the notification to read it, you'll find a link in the bottom right that says "Stop notifying me". Click this link if you don't wish to be notified about this any longer. See the screenshot below.
To read more about notifications and to watch a great video of how to control all your inbox notifications, go to the Managing your notifications article.