Wonder Grove uses short animated videos to teach various social skills through stories with recurring characters. The website also includes corresponding lesson plans, coloring/activity pages, and other resources.
The author of this blog is the mother of a child with autism who struggled for a long time to find an inexpensive, effective app for creating personalized social stories for her son. After she had written an initial blog post about this gap in the market, a company stepped up and created Kid in Story. This blog post is a follow-up in which she describes and praises this new app that has met her family's needs. This is a great, detailed read about a useful tool.
The Autism Research Institute has provided this guide to social stories. While it is not specific to digital applications, it is a great resource to help you compose the text of your social stories. It talks about the different types of sentences that social stories should include and the purpose of each. This will help you to write social stories in the most effective language possible.