If you’re using Google Reader to manage your RSS feeds, a handy feature is Google Trends. This keeps track of your feed activity on a day to day basis.
Trends keeps track of your most read feeds as well as what days and what times you read them. This becomes handy if you want to keep track of how your feeds are working for you.
Probably the most useful feature so far is Subscription Trends, which keeps track of the most frequently updated feeds and those that are inactive.
Check the Inactive tab to see what feeds you may have subscribed to in the past that are no longer being updated. From here you can unsubscribe from each feed by hitting the Trash icon.
Simple and quick feed management.
Reader - [Google]