A categorized collection of awesome opensource unity3d repos (including with some projects that related to game development)

• 2D
• AI
• Camera
• Character Controllers 2D
• Character Controllers 3D
• Crypto
• Editor
• Effect
• Framework
• Input
• Lua
• Monetization
• Networking
• Plugins
• Procedural Generation Systems
• Pooling System
• Services
• Sounds
• Tweening
• UI
• Utilities
• VR

• UnityTiled - Editor tools for working with Tiled maps in Unity.
• Unity2D-Components - A constantly evolving array of Unity C# components for 2D games, including classes for pixel art cameras, events & messaging, saving & loading game data, collision handlers, object pools, and more.
• 2DTileMapLevelEditor - 2D Tile Map Level Editor for Unity

• Unity Movement AI - A library of common movement AI scripts known as Steering Behaviors. You can use these scripts to help your NPCs move around your game.

• Unity Pixel Camera - A resolution independent pixel perfect camera for Unity
• DeadSimple Pixel-Perfect Camera - An exceedingly easy-to-use pixel perfect orthographic camera script for 2D scenes in Unity. Punch in a few specs and you've got a working pixel perfect camera. It's that easy.

• Unity 2D Platformer Controller - A customizable 2D platformer motor that handles mechanics such as double jumps, wall jumps, and corner grabs. Includes a player controlled prefab that can be dropped into any scene for immediate support.
• CharacterController2D - is similar to the built-in Unity CharacterController component. It has a similar API (mainly a move method that takes a delta movement) and provides a firm base with which to make a super solid controller using Unity's 2D system.
• Unity 2D Platformer Controller - A customizable 2D platformer motor that handles mechanics such as double jumps, wall jumps, and corner grabs. Includes a player controlled prefab that can be dropped into any scene for immediate support.

• SuperCharacterController - Custom Character Controller for Unity. Fulfills all common character controller functions such as collision detection and pushback, slope limiting and collider ignoring.
• Unity-ThirdPersonController - Third Person Controller for Unity (with custom gravity)

• Bouncy Castle C# With Unity3d Supports - Bouncy Castle C# With Unity3d Supports

• Unity-QuickSheet - Unity-QuickSheet enables you to use spreadsheet file data within Unity editor.
• Unity3D Rainbow Folders - This asset allows you to set custom icons for any folder in unity project browser.
• Reorderable List Editor Field for Unity - Reorderable List Editor Field for Unity
• Reorderable Inspector - Automatic reorderable lists for Unity game engine components
• Vexe Framework (VFW) - an editor extension that offers much more advance editor extensibility features than what comes out of the box with Unity.
• Tidy Up - Neat little tool! to help you keep your Unity projects organised by throwing assets in their designated folders.
• Unity Psd Importer - Advanced PSD importer for Unity3D
• property-drawer-collection
• unity-symlink-utility - A small extension that adds a menu item to add folders as symlinks in Unity
• giles - GILES: A Runtime Level Editor for Unity3D
• UnityDefineManager - Easily manage global defines in Unity
• consolation - In-game debug console for Unity.
• HexTiles - Unity Hex Tile Editor

• Time Of Day System Free - With this package you can create Basic Day/Night cycle, also it includes a system of curves and gradients to control the parameters of the lighting, sky, moon, stars, fog, etc.
• Unity 5 Effects - Effect storage space for Unity 5.
• Outline-Effect - Outline Image Effect for Unity

• Zenject - Dependency Injection Framework for Unity3D
• UniRx - Reactive Extensions for Unity
• Fungus - https://github.com/snozbot/fungus
• Node_Editor_Framework - Node Editor framework for Unity3D
• Entitas-CSharp - Entitas is a super fast Entity Component System (ECS) Framework specifically made for C# and Unity

• InputManager - Custom InputManager for Unity
• InControl - An input manager for Unity that tames the cross-platform controller beast.
• InputBinder - Easily bind input events to methods in Unity.
• TouchKit - Gestures and input handling made sane for Unity
• TouchScript (Recommend) - Complete multitouch solution for Unity: Win8, TUIO, Mobile.

• slua (Recommend) - Fastest lua binding via static code generating for Unity3D and mono.
• xLua (Recommend) - xLua is a hot-fix solution plugin for Unity3D, it supports android, ios, windows, osx, etc.
• UniLua - A pure C# implementation of Lua 5.2 focus on compatibility with Unity3D.
• MoonSharp - An interpreter for the Lua language, written entirely in C# for the .NET, Mono, Xamarin and Unity3D platforms, including handy remote debugger facilities

• unity3d-levelup - Unity3D F2P game progression library - worlds, levels, missions, scores, records and more. Part of The SOOMLA Framework - for game design, economy modeling and faster development.
• unity3d-store - Unity in-app purchase & virtual economy library. Part of The SOOMLA Framework - for game design, economy modeling and faster development.
• Google Mobile Ads Unity Plugin - Official Unity Plugin for the Google Mobile Ads SDK

• UnitySocketIO - socket.io client for unity3d.
• websocket-sharp - A C# implementation of the WebSocket protocol client and server
• Hazel-Networking - A low level networking library for C# providing connection orientated, message based communication via TCP, UDP and RUDP.
• MassiveNet - Unity3d UDP networking library focused on high-CCU, multi-server architecture.
• unet-hlapi-manager - The simple network manager based on Unity's NetworkManager without players, scenes stuffs focus on network messages callback handles. Intenly made for multiple server purposes
• Nakama - An open-source distributed social and realtime server for games and apps by Heroic Labs. It includes a large set of services for users, data storage, and realtime client/server communication; as well as specialized APIs like realtime multiplayer, groups/guilds, and chat.
• Barebones Master Server - Master Server framework for Unity
• Forge Networking Remastered - In short, Forge Networking is a free and open source multiplayer game (multi-user) networking system that has a very good integration with the Unity game engine. You wanna make a multiplayer game or real time multi-user application? This is the library for you.
• Facepunch.Steamworks - Another fucking c# Steamworks implementation
• MagicOnion - gRPC based HTTP/2 RPC Streaming Framework for .NET, .NET Core and Unity.

• Reign Unity Plugin - This Reign API is a cross-platform, unified API for the Unity game engine.
• unity-webview - A plugin for Unity 5 that overlays WebView components on Unity view. It works on Android, iOS, Unity Web Player, and OS X (Windows is not supported for now).

• ProceduralToolkit - Instruments for development of procedural generation systems in Unity game engine
• DungeonGenerator - A dungeon generator for Unity

• Unity-QuickPool - Simple pooling toolkit for Unity game engine
• RecyclerKit - Object pool manager for Unity

• protobuf-net - Protocol Buffers library for idiomatic .NET

• Google Play Games plugin for Unity - Google Play Games plugin for Unity

• usfxr - a C# library used to generate and play game-like procedural audio effects inside Unity. With usfxr, one can easily design and synthesize original sound in real time for actions such as item pickups, jumps, lasers, hits, explosions, and more, without ever leaving the Unity editor.
• Unity-Beat-Detection - Musical beat detection and audio spectrum analysis for use with the Unity game engine.

• DOTween (Recommend) - A Unity C# animation engine. HOTween v2
• LeanTween - LeanTween is an efficient animation engine for Unity
• GoKit - Lightweight tween library for Unity

• FairyGUI-unity - A flexible UI framework for Unity
• MiniMap - Unity3D mini map (radar) system (Asset Store link - https://www.assetstore.unity3d.com/en/#!/content/33729 )
• LoopScrollRect - UGUI ScrollRect reusing cells, to improve performance, loading time and draw calls.
• MaterialUI - MaterialUI is a UI kit for Unity that follows Google's official material design guidelines.
• Unity-UI-Extensions
• EnhancedScrollView - Cool 3d scoll view for Unity(NGUI 3D UGUI support)
• Beautiful Text Outline for Unity UI - Beautiful text outline for Unity UI.

• LINQ to GameObject - Traverse GameObject Hierarchy by LINQ
• Moments - A quick GIF replay recorder for Unity
• UniGif - GIF image decoder for Unity.
• unityassets - Assorted assets previously on sale on the Unity Asset Store, now free on github.
• UnityToolbag - Variety of Unity scripts and tools.
• C-Sharp-Promise - Promises library for C# for management of asynchronous operations.
• 3DMath - Unity C# 3D Math methods library.
• Projeny - A project and package manager for Unity.
• Unity Size Explorer - Visualize how much space each asset in your Unity game takes and quickly optimize your game's file size.
• Spine Runtimes - Collection of Spine runtimes including with Unity3d version.
• UnityStudio - Unity Studio is a tool for exploring, extracting and exporting assets from Unity games and apps.
• InGameReplay - Allow you to record the transform of any objects to replay it

• VRTK - A productive VR Toolkit for rapidly building VR solutions in Unity3d.