If 2D gameplay is fine, you might consider the Scrolling Game Development Kit. (version 2.0) This is a fairly light-weight suite of game development tools focused on simpler 2D titles. It is great for platformers, and can be used for puzzle games as well. It has a visual IDE for editing and sprite / scene management, and…
Do you know Flixel? It might be exactly what you are looking for since you are going with flash. http://flixel.org/ Check out the example games included, they are awesome.