Hello everybody!
With the ongoing success of the Humble GameMaker Bundle we're seeing a huge influx of new users, many of whom are opening the software for the very first time. So if that's you reading this, hello! I'm Shaun, your Community Manager. Great to have you on board.
GameMaker is a very powerful and flexible tool. As a result, depending on what you want to achieve you might want some direction to get you started. Fortunately there is a huge wealth of information and tutorials available. Here are some that we recommend:
Many YouTubers (myself included!) run channels dedicated to GameMaker tutorial content. These range from beginner introductions to specific topics. Here is a choice selection of content great for beginners:
GameMaker comes with a ton of tutorial and demo content available directly from the launcher covering a wide variety of topics. Just select the tutorials tab from the launcher as shown below:

if you're stuck on something specific you might be able to get some help directly from our thriving community:
There's so much more great content out there, but hopefully this short list offers you some places to start. Whatever your goals we hope you all have a great time with GameMaker: Studio and we look forward to seeing what you can build!
Best of luck!
Shaun Spalding, Community Manager