Ok - regular readers know already I LOVE Popfly - it's just an amazingly cool idea for a platform with great UI. But the team has just outdone themselves with Popfly Game Creator the Popfly way to make games! Just like with the GUI for making mashups this game maker relies primary with a drag and drop interface with a few field where you can modify numerical values. This is by no means a playground where you can do no wrong - debugging etc is still very much required (why isn't my ship moving fast enough?) However, it makes the process accessible enough that you can learn the system while creating - this is key.
There's a great mix of pre-made graphics with good selection and quality of the finished product. The first game I made (10 mins in the morning) was a type of modified space invaders:
The control interface is even better. Beautiful layout and sound effects in a "programming environment". Awesome. You gotta check it out!