Within the last 24 hours, I received something like 24 Yearling badges. This cluttered up my achievements dropdown, needless to say. Is there something like a clear all or read all function to either acknowledge all these at once or to clear them? Something like Facebook when the list of haven't seens builds up?
This feature doesn't exist, but since this is a one-time event and only the last 100 or so achievements are shown, you can quickly get rid of them by continuing to contribute to the Stack Exchange sites. In the 6-8 weeks it would take to build such a feature, they'll probably be buried anyway. In some sense, you acknowledge them by clicking on the green trophy in the top bar; after that, it will return to its normal gray state.