When you view a cluster in Google News, there's a new option to filter sources: you can restrict news articles to blogs and to local news sites that are relevant to your query. The filters are a good way to find opinionated articles and more up-to-date information from local sites.
Here's an example of cluster that groups articles about some new information regarding last week's Qantas Airways flight that was forced to make an emergency landing in Manila. Google shows three filters: blogs, Australia (Qantas is the national airline of Australia) and Manila, Philippines.
There's also a search box that is supposed to let you find articles from the cluster, but it doesn't work properly right now.