Free Assets

• Unity Asset Store Free Assets includes free things in every category. You can always filter search results by FREE to see what’s available.
• Must-have free assets from the Unity store

Scripts

• Unity Wiki has tons of great scripts and shaders provided as example code.

Textures

• Google Image Search with the keywords “texture” and “repeating” often has results.
• All CG Textures has quality free textures.

3D models

• Sketchup 3D Warehouse is the largest library of free 3D models in Sketchup format. You can download freely and use in your games. You can also upload your own creations to 3D Warehouse.
• Yobi3D is a 3D model search engine. You can search with simple keywords and see the results in 3D.
• CGTrader has a list of free models

3D Character Rigs

• Creative Crash has many free 3D character rigs in Maya format.

Audio sounds

• FreeSound Project is a searchable library of free sound files that you can use in your games. You can also upload your sounds to FreeSound for others to use.
• Free Music Archive is a library of free Creative Commons-licensed music.