AR

Wikitude

• AR
• Augmented Reality
• Mobile

Not free, but you can use it developer mode to create compelling image-based Augmented Reality experiences. Great tool

AR Studio

• AR

Tools to help you create Augmented experiences.

3D Tiles

• AR
• VR

A library to be used with AR/VR tool A-Frame that provides the ability to import 3D panorama frames.

Echoes AR Walks

• AR
• Audio

Create AR audio walks with this tool.

Spark AR

• AR
• Desktop

A desktop tool with which you can create 3D Augmented Reality apps that do face tracking and other cool AR features. You can create interactive patches using a visual flow language or code in Javascript.

Search for XR/AR content

• AR
• VR

A search engine to find XR sites.

Eyejack

• AR
• Desktop

An app with which to make AR (Mac)

Pictarize

• AR

Fabulous, free, AR making tool. 

Coldspotting AR

• AR
• iOS

VR Scout

• AR
• VR

A huges collection of articles about AR and VR projects