Responsive Sizer helps implement a responsive layout by providing helper widgets and extensions. Responsive_sizer has a lot of improvements over the unmaintained sizer package:

A Few Good Examples Of Widgets For Flutter

A nice collection of flutter widgets

A widget that allow user resize the widget with drag

Widget, that can make any static located widget hidable (scroll to hide)

A widget for stacking cards, which users can swipe horizontally and vertically with beautiful animations.

A set of utilities that allow you to easily consume a Redux Store to build Flutter Widgets.

A Flutter plugin that provides a WebView widget

A flutter package from AsurRaa for widgets and utility functions.

A Flutter widget that imposes different constraints on its child than it gets from its parent

A Flutter package for inspecting widgets

A flutter package supports drag & drop widgets inside the GridView.builder for multiplatform

A code generator to write widgets as function without loosing the benefits of classes.

A collection of Login Screens, Buttons, Loaders and Widgets with attractive UIs built with Flutter

Interactive Widgets For Flutter

An alternative to Overlay which allows you to easily render and hit test a widget outside its parent bounds

Experimental solution for web-like text selection across widgets (text, images, et cetera).

Widget for displaying waves with custom color, duration, floating and blur effects.

A widget for swiping through a deck of cards with gestures or buttons.

Scratch card widget which temporarily hides content from user.