Here is a list of Multi Device Website Mockup Generators and resources:

1. TechSini Multi Mockup: This tool allows you to test your responsive website on Apple devices, including Apple iMac, MacBook, iPad, and iPhone.
2. Website Mockup Generator: It helps create free mockups of your website on various devices in seconds.
3. Gemoo: This tool can generate multi-device website mockups, including desktop computers and mobile phones.
4. Yujin Yeoh’s Website Mockup Generator: A free online tool for testing your responsive website on Apple devices.
5. Responsive Mockups: This generator creates responsive, portfolio-ready mockups with just a URL.
6. MediaModifier: Offers multi-device mockup templates for promoting your website or application. Source
7. Webnots: Provides five free mockup generator tools to create device mockups.
8. Cohoda’s Blog: Lists the tools they use to generate mockups.
9. BannerBear: Offers a guide on how to make a device mockup generator for websites.
10. Artboard Studio: You can create website mockups for free with their online website mockup generator.

Please note that the effectiveness and features of these tools may vary, and it’s recommended to explore each one to find what best suits your needs.