http://pttrns.com/ http://pttrns.com/ & http://mobile-patterns.com/ http://mobile-patterns.com/ have screen captures of top apps, grouped by pattern, like Activ

http://pttrns.com/ http://pttrns.com/ & http://mobile-patterns.com/ http://mobile-patterns.com/ have screen captures of top apps, grouped by pattern, like Activity Feed, Sign In, Empty Data Sets, etc.