UiPath Studio: Community Edition (free, fully featured and extensible). You will need it in order to create and test snippets, connectors, automation frameworks, dashboards, machine learning models, and custom activities.
Microsoft Visual Studio with the .NET desktop development workload installed and NuGet Package Explorer for developing custom activities. Check here the full tutorial. This is mandatory only for developing custom activities in C#.
UiPath Academy - check out the online, free of charge RPA Developer and Solution Architect courses.
UiPath Knowledge Base - in the resource section you can find all the available knowledge to get you up to speed.
Video tutorials - Get familiarized with our technology as fast as possible in small chunks of knowledge delivered in video format.
UiPath Community - a compressive knowledge base about our technology.
Here you can find all the submissions during the idea contest to serve you as an inspiration! Two Live Webinars (dates TBD):
Understanding the UiPath Technologies
What is a reusable component? How does it look?
MIT open source license information