XCodeClub.com - Rent your own private Virtual Mac with latest XCode.
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
VirtualMacOSX.com - vmOSX -- is your affordable, Mac-based home on the web.
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
MacinCloud - MacinCloud is a Mac cloud platform that provides on-demand Mac cloud servers, flexible dev workload infrastructure and comprehensive Mac in the Cloud solutions
Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.