There are lots of icons that you can use for free and these are my list that helps me doing my design works.
There are so many prototyping tools that keeps on popping up so I want to list all the prototyping tools based on their category (Page-based or Layer-based).
Created for designers, by designers, InVision is a prototyping, collaboration and workflow tool. InVision gives you clarity, collaboration, and control of everything you need to power your design process. It allows you to efficiently and simply create interactive mockups for your wireframes and designs. When you have completed adding all the pages and elements to your prototype you can then share it with your team or clients for feedback.