DLToolkit Controls for Xamarin.Forms 
Examples:
https://github.com/daniel-luberda/DLToolkit.Forms.Controls/tree/master/Samples (Example project uses xamvvm MVVM toolkit from here)
TIP: Clone repo, open the solution, build it and run sample app. Also visit my blog: http://daniel-luberda.github.io
Available controls:
- FFImageLoading - Library to load / cache / transform images on iOS, Android, Windows and Xamarin.Forms. Details
- FlowListView - ListView derivative with flowing, grid-like columns support. Details / NuGet
- ImageCropView - Image cropper. Details / NuGet
- TagEntryView - Flowing entry with tags/badges support. Details / NuGet