Clickteam
Clickteam developed The Games Factory (TGF) and Multimedia Fusion (MMF), both of which are the popular choices for game development on MFGG. They are also responsible for older game creaton tools, "Klik and Play" (KNP) and "Click 'n' Create" (CNC), as well as Multimedia Fusion Express (MMFE). Currently in the works are TGF2 and MMF2. You may find these tools as well as others at http://www.clickteam.com and may also download some tutorials for them at MFGG's site.
Unlike GameMaker (Another popular choice for creating fangames), Clickteam's products require you to purchase the registered versions of some of their products. Trial versions are available through clickteam's website, but after the trial period runs out, a purchase is required to continue making games. The trial versions also do not allow stand alone applications to be created, so the games are unplayable unless the player owns the product used to make the game.
The games, libs, and how-to's on the main site are primarily made with either of these programs.
