LINQ to GameObject is GameObject extensions for Unity that allows traverse hierarchy and append GameObject like LINQ to XML.
The concept of LINQ to GameObject is axis on tree, you can traverse with Children, Ancestors, Descendants, BeforeSelf, AfterSelf. Every traverse method returns IEnumerable[GameObject] and deferred exectuion.
This library is free and opensource on GitHub. More info, supports and sourcecodes, see https://github.com/neuecc/LINQ-to-GameObject-for-Unity
This library supports all platforms(PC/iOS/Android/WP8/Windows Store App/Mac, etc).
Unity forum support thread is here, ask me any questions - http://forum.unity3d.com/threads/linq-to-gameobject.292611/
LINQ to GameObject supports Unity 5 and uGUI's RectTransform.