From the web to games
Python's Pygame is certainly a good choice as others have said. If you want to get in to deep video game programming though.. move on to something like C++ or another lower level language.. from experience, most higher level languages tend to put artificial hurdles up in regards to decent video games. Though for a simple 2d game you cant go wrong with python.
another decent environment to use is Ogre3d, but you would need C++ or the PyOgre bindings (which are not up to date, but I hear they do work okay).
Going from web to game design really is a decent step, as long as you have a good sense of design. the physics and game logic can be learned, but ive yet to see anyone who could properly learn how to write a decent GUI.. as is seen in most cases these days, the final GUI lay out tends to be a process of elimination or beta with trial and error.
Only suggestion i have left is keep your game logic as far away as possible from your graphics. Be Modular.
-edit-
oh and a note.. stay away from Tkinter in python for anything more than a simple tool.. I have found it most frustrating to use. there is wxPython, GTK, pygame, and PyQT.. and all of them (in my opinion) are far better graphic frameworks.
I'm a basic web developer. I know PHP, a little bit of Python and Ruby. JavaScript as well [some stuff]. I'm not a hardcore developer. I know what it takes do develop most of web cases.
Now, I have this desire to go deeper and start developing games. I know it sounds a huge leap, but that is why I'm asking here. I already have some games ideas. It would be simple 2d plataform games, and I would like to know what is the best way to start.
I don't want to start with Flash. I'm looking for working with other stuff. I already started to look around for the Unity 3D framework and UDK, but I just don't know how to get started.
So, any hints, tips or sugestions to make?